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	$126.72	3.472%	$131.1197	$131.12	$131.10	$131.10
Purchase #2	$137.74	8.387%	$149.2923	$149.29	$149.30	$149.30
Purchase #3	$209.50	11.253%	$233.075	$233.08	$233.10	$233.10
Purchase #4	$229.70	3.159%	$236.9562	$236.96	$236.95	$237.00
Purchase #5	$13.52	13.651%	$15.3656	$15.37	$15.35	$15.40
Purchase #6	$32.38	6.573%	$34.5083	$34.51	$34.50	$34.50
Purchase #7	$134.30	12.804%	$151.4958	$151.50	$151.50	$151.50
7 purchase totals =	$883.86		$951.8129	$951.83	$951.80	$951.90