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	$190.81	11.235%	$212.2475	$212.25	$212.25	$212.20
Purchase #2	$94.95	9.238%	$103.7215	$103.72	$103.70	$103.70
Purchase #3	$125.56	4.575%	$131.3044	$131.30	$131.30	$131.30
Purchase #4	$92.55	5.828%	$97.9438	$97.94	$97.95	$97.90
Purchase #5	$117.58	5.607%	$124.1727	$124.17	$124.15	$124.20
Purchase #6	$111.37	4.417%	$116.2892	$116.29	$116.30	$116.30
Purchase #7	$98.49	13.424%	$111.7113	$111.71	$111.70	$111.70
7 purchase totals =	$831.31		$897.3904	$897.38	$897.35	$897.30