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	$93.95	7.130%	$100.6486	$100.65	$100.65	$100.60
Purchase #2	$16.58	10.435%	$18.3101	$18.31	$18.30	$18.30
Purchase #3	$198.85	12.581%	$223.8673	$223.87	$223.85	$223.90
Purchase #4	$167.91	12.458%	$188.8282	$188.83	$188.85	$188.80
Purchase #5	$216.57	8.293%	$234.5302	$234.53	$234.55	$234.50
Purchase #6	$93.93	12.665%	$105.8262	$105.83	$105.85	$105.80
Purchase #7	$242.42	13.388%	$274.8752	$274.88	$274.90	$274.90
7 purchase totals =	$1,030.21		$1,146.8858	$1,146.90	$1,146.95	$1,146.80