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	$53.59	11.601%	$59.807	$59.81	$59.80	$59.80
Purchase #2	$222.47	13.865%	$253.3155	$253.32	$253.30	$253.30
Purchase #3	$115.85	11.578%	$129.2631	$129.26	$129.25	$129.30
Purchase #4	$133.33	13.634%	$151.5082	$151.51	$151.50	$151.50
Purchase #5	$181.93	13.420%	$206.345	$206.35	$206.35	$206.30
Purchase #6	$128.82	9.704%	$141.3207	$141.32	$141.30	$141.30
Purchase #7	$195.97	8.457%	$212.5432	$212.54	$212.55	$212.50
7 purchase totals =	$1,031.96		$1,154.1027	$1,154.11	$1,154.05	$1,154.00