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	$143.69	13.303%	$162.8051	$162.81	$162.80	$162.80
Purchase #2	$167.95	13.294%	$190.2773	$190.28	$190.30	$190.30
Purchase #3	$34.83	13.502%	$39.5327	$39.53	$39.55	$39.50
Purchase #4	$130.26	8.573%	$141.4272	$141.43	$141.45	$141.40
Purchase #5	$39.64	12.312%	$44.5205	$44.52	$44.50	$44.50
Purchase #6	$172.54	3.805%	$179.1051	$179.11	$179.10	$179.10
Purchase #7	$232.55	11.267%	$258.7514	$258.75	$258.75	$258.80
7 purchase totals =	$921.46		$1,016.4193	$1,016.43	$1,016.45	$1,016.40