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	$121.76	4.582%	$127.339	$127.34	$127.35	$127.30
Purchase #2	$243.58	3.286%	$251.584	$251.58	$251.60	$251.60
Purchase #3	$214.26	3.700%	$222.1876	$222.19	$222.20	$222.20
Purchase #4	$226.75	4.650%	$237.2939	$237.29	$237.30	$237.30
Purchase #5	$247.57	4.348%	$258.3343	$258.33	$258.35	$258.30
Purchase #6	$228.76	12.140%	$256.5315	$256.53	$256.55	$256.50
Purchase #7	$155.46	3.253%	$160.5171	$160.52	$160.50	$160.50
7 purchase totals =	$1,438.14		$1,513.7874	$1,513.78	$1,513.85	$1,513.70