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	$54.77	10.557%	$60.5521	$60.55	$60.55	$60.60
Purchase #2	$49.80	8.821%	$54.1929	$54.19	$54.20	$54.20
Purchase #3	$75.34	9.198%	$82.2698	$82.27	$82.25	$82.30
Purchase #4	$36.38	11.341%	$40.5059	$40.51	$40.50	$40.50
Purchase #5	$204.83	8.647%	$222.5417	$222.54	$222.55	$222.50
Purchase #6	$235.47	12.321%	$264.4823	$264.48	$264.50	$264.50
Purchase #7	$218.59	13.727%	$248.5958	$248.60	$248.60	$248.60
7 purchase totals =	$875.18		$973.1405	$973.14	$973.15	$973.20