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	$243.44	9.632%	$266.8881	$266.89	$266.90	$266.90
Purchase #2	$176.72	4.144%	$184.0433	$184.04	$184.05	$184.00
Purchase #3	$102.59	9.165%	$111.9924	$111.99	$112.00	$112.00
Purchase #4	$98.54	5.343%	$103.805	$103.81	$103.80	$103.80
Purchase #5	$79.71	12.113%	$89.3653	$89.37	$89.35	$89.40
Purchase #6	$56.87	9.485%	$62.2641	$62.26	$62.25	$62.30
Purchase #7	$103.64	7.669%	$111.5882	$111.59	$111.60	$111.60
7 purchase totals =	$861.51		$929.9464	$929.95	$929.95	$930.00