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	$186.80	4.792%	$195.7515	$195.75	$195.75	$195.80
Purchase #2	$166.49	11.541%	$185.7046	$185.70	$185.70	$185.70
Purchase #3	$206.60	7.579%	$222.2582	$222.26	$222.25	$222.30
Purchase #4	$223.78	12.528%	$251.8152	$251.82	$251.80	$251.80
Purchase #5	$11.31	5.539%	$11.9365	$11.94	$11.95	$11.90
Purchase #6	$185.33	6.468%	$197.3171	$197.32	$197.30	$197.30
Purchase #7	$57.27	9.175%	$62.5245	$62.52	$62.50	$62.50
7 purchase totals =	$1,037.58		$1,127.3076	$1,127.31	$1,127.25	$1,127.30