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	$235.71	8.364%	$255.4248	$255.42	$255.40	$255.40
Purchase #2	$124.34	8.140%	$134.4613	$134.46	$134.45	$134.50
Purchase #3	$21.66	4.146%	$22.558	$22.56	$22.55	$22.60
Purchase #4	$136.84	13.533%	$155.3586	$155.36	$155.35	$155.40
Purchase #5	$52.48	4.617%	$54.903	$54.90	$54.90	$54.90
Purchase #6	$33.81	7.445%	$36.3272	$36.33	$36.35	$36.30
Purchase #7	$90.28	5.751%	$95.472	$95.47	$95.45	$95.50
7 purchase totals =	$695.12		$754.5049	$754.50	$754.45	$754.60