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	$51.79	12.103%	$58.0581	$58.06	$58.05	$58.10
Purchase #2	$141.93	4.642%	$148.5184	$148.52	$148.50	$148.50
Purchase #3	$231.53	6.405%	$246.3595	$246.36	$246.35	$246.40
Purchase #4	$218.72	11.616%	$244.1265	$244.13	$244.15	$244.10
Purchase #5	$38.45	11.172%	$42.7456	$42.75	$42.75	$42.70
Purchase #6	$211.59	10.189%	$233.1489	$233.15	$233.15	$233.10
Purchase #7	$84.44	6.334%	$89.7884	$89.79	$89.80	$89.80
7 purchase totals =	$978.45		$1,062.7454	$1,062.76	$1,062.75	$1,062.70