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	$42.69	9.307%	$46.6632	$46.66	$46.65	$46.70
Purchase #2	$141.98	11.766%	$158.6854	$158.69	$158.70	$158.70
Purchase #3	$62.63	7.791%	$67.5095	$67.51	$67.50	$67.50
Purchase #4	$21.68	12.160%	$24.3163	$24.32	$24.30	$24.30
Purchase #5	$247.88	9.457%	$271.322	$271.32	$271.30	$271.30
Purchase #6	$130.91	6.615%	$139.5697	$139.57	$139.55	$139.60
Purchase #7	$223.72	9.702%	$245.4253	$245.43	$245.45	$245.40
7 purchase totals =	$871.49		$953.4914	$953.50	$953.45	$953.50