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	$197.46	12.731%	$222.5986	$222.60	$222.60	$222.60
Purchase #2	$37.51	5.317%	$39.5044	$39.50	$39.50	$39.50
Purchase #3	$101.61	9.237%	$110.9957	$111.00	$111.00	$111.00
Purchase #4	$93.78	6.487%	$99.8635	$99.86	$99.85	$99.90
Purchase #5	$74.46	11.640%	$83.1271	$83.13	$83.15	$83.10
Purchase #6	$34.59	4.157%	$36.0279	$36.03	$36.05	$36.00
Purchase #7	$105.95	9.204%	$115.7016	$115.70	$115.70	$115.70
7 purchase totals =	$645.36		$707.8188	$707.82	$707.85	$707.80