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	$166.41	10.733%	$184.2708	$184.27	$184.25	$184.30
Purchase #2	$241.33	6.801%	$257.7429	$257.74	$257.75	$257.70
Purchase #3	$99.36	10.178%	$109.4729	$109.47	$109.45	$109.50
Purchase #4	$43.89	7.616%	$47.2327	$47.23	$47.25	$47.20
Purchase #5	$227.27	11.573%	$253.572	$253.57	$253.55	$253.60
Purchase #6	$91.71	8.538%	$99.5402	$99.54	$99.55	$99.50
Purchase #7	$6.78	5.293%	$7.1389	$7.14	$7.15	$7.10
7 purchase totals =	$876.75		$958.9704	$958.96	$958.95	$958.90