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	$110.32	12.869%	$124.5171	$124.52	$124.50	$124.50
Purchase #2	$144.38	10.643%	$159.7464	$159.75	$159.75	$159.70
Purchase #3	$224.69	5.761%	$237.6344	$237.63	$237.65	$237.60
Purchase #4	$55.77	13.639%	$63.3765	$63.38	$63.40	$63.40
Purchase #5	$181.27	9.516%	$198.5197	$198.52	$198.50	$198.50
Purchase #6	$87.28	13.733%	$99.2662	$99.27	$99.25	$99.30
Purchase #7	$173.76	9.797%	$190.7833	$190.78	$190.80	$190.80
7 purchase totals =	$977.47		$1,073.8436	$1,073.85	$1,073.85	$1,073.80