Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$72.28	12.525%	$81.3331	$81.33	$81.35	$81.30
Purchase #2	$97.93	13.763%	$111.4081	$111.41	$111.40	$111.40
Purchase #3	$204.86	3.665%	$212.3681	$212.37	$212.35	$212.40
Purchase #4	$187.61	12.353%	$210.7855	$210.79	$210.80	$210.80
Purchase #5	$63.97	10.232%	$70.5154	$70.52	$70.50	$70.50
Purchase #6	$150.91	13.352%	$171.0595	$171.06	$171.05	$171.10
Purchase #7	$181.47	4.216%	$189.1208	$189.12	$189.10	$189.10
7 purchase totals =	$959.03		$1,046.5905	$1,046.60	$1,046.55	$1,046.60