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	$234.75	9.255%	$256.4761	$256.48	$256.50	$256.50
Purchase #2	$241.81	11.355%	$269.2675	$269.27	$269.25	$269.30
Purchase #3	$199.78	9.452%	$218.6632	$218.66	$218.65	$218.70
Purchase #4	$40.37	13.703%	$45.9019	$45.90	$45.90	$45.90
Purchase #5	$179.27	13.523%	$203.5127	$203.51	$203.50	$203.50
Purchase #6	$142.34	3.797%	$147.7446	$147.74	$147.75	$147.70
Purchase #7	$50.41	8.619%	$54.7548	$54.75	$54.75	$54.80
7 purchase totals =	$1,088.73		$1,196.3208	$1,196.31	$1,196.30	$1,196.40