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	$115.87	7.133%	$124.135	$124.14	$124.15	$124.10
Purchase #2	$33.82	9.587%	$37.0623	$37.06	$37.05	$37.10
Purchase #3	$187.26	13.153%	$211.8903	$211.89	$211.90	$211.90
Purchase #4	$240.64	6.427%	$256.1059	$256.11	$256.10	$256.10
Purchase #5	$105.32	10.639%	$116.525	$116.53	$116.55	$116.50
Purchase #6	$106.30	4.795%	$111.3971	$111.40	$111.40	$111.40
Purchase #7	$190.73	9.327%	$208.5194	$208.52	$208.50	$208.50
7 purchase totals =	$979.94		$1,065.6350	$1,065.65	$1,065.65	$1,065.60