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	$133.33	13.862%	$151.8122	$151.81	$151.80	$151.80
Purchase #2	$140.35	10.817%	$155.5317	$155.53	$155.55	$155.50
Purchase #3	$231.63	5.573%	$244.5387	$244.54	$244.55	$244.50
Purchase #4	$90.48	6.572%	$96.4263	$96.43	$96.45	$96.40
Purchase #5	$226.66	13.148%	$256.4613	$256.46	$256.45	$256.50
Purchase #6	$115.85	13.713%	$131.7365	$131.74	$131.75	$131.70
Purchase #7	$32.86	7.810%	$35.4264	$35.43	$35.45	$35.40
7 purchase totals =	$971.16		$1,071.9331	$1,071.94	$1,072.00	$1,071.80