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	$64.52	3.339%	$66.6743	$66.67	$66.65	$66.70
Purchase #2	$101.48	9.627%	$111.2495	$111.25	$111.25	$111.20
Purchase #3	$93.75	6.476%	$99.8213	$99.82	$99.80	$99.80
Purchase #4	$48.86	4.197%	$50.9107	$50.91	$50.90	$50.90
Purchase #5	$104.95	5.332%	$110.5459	$110.55	$110.55	$110.50
Purchase #6	$215.64	3.530%	$223.2521	$223.25	$223.25	$223.30
Purchase #7	$84.36	6.463%	$89.8122	$89.81	$89.80	$89.80
7 purchase totals =	$713.56		$752.2660	$752.26	$752.20	$752.20