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	$200.67	9.710%	$220.1551	$220.16	$220.15	$220.20
Purchase #2	$58.70	5.111%	$61.7002	$61.70	$61.70	$61.70
Purchase #3	$64.42	10.249%	$71.0224	$71.02	$71.00	$71.00
Purchase #4	$11.54	10.460%	$12.7471	$12.75	$12.75	$12.70
Purchase #5	$33.48	7.716%	$36.0633	$36.06	$36.05	$36.10
Purchase #6	$40.65	12.308%	$45.6532	$45.65	$45.65	$45.70
Purchase #7	$33.97	11.262%	$37.7957	$37.80	$37.80	$37.80
7 purchase totals =	$443.43		$485.1370	$485.14	$485.10	$485.20