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	$102.51	7.836%	$110.5427	$110.54	$110.55	$110.50
Purchase #2	$137.94	10.547%	$152.4885	$152.49	$152.50	$152.50
Purchase #3	$214.75	9.519%	$235.1921	$235.19	$235.20	$235.20
Purchase #4	$191.27	7.645%	$205.8926	$205.89	$205.90	$205.90
Purchase #5	$130.31	8.456%	$141.329	$141.33	$141.35	$141.30
Purchase #6	$54.28	13.244%	$61.4688	$61.47	$61.45	$61.50
Purchase #7	$74.71	10.336%	$82.432	$82.43	$82.45	$82.40
7 purchase totals =	$905.77		$989.3457	$989.34	$989.40	$989.30