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	$79.87	12.305%	$89.698	$89.70	$89.70	$89.70
Purchase #2	$169.89	12.817%	$191.6648	$191.66	$191.65	$191.70
Purchase #3	$124.44	12.451%	$139.934	$139.93	$139.95	$139.90
Purchase #4	$212.85	4.436%	$222.292	$222.29	$222.30	$222.30
Purchase #5	$236.32	8.559%	$256.5466	$256.55	$256.55	$256.50
Purchase #6	$235.63	10.715%	$260.8778	$260.88	$260.90	$260.90
Purchase #7	$201.37	4.830%	$211.0962	$211.10	$211.10	$211.10
7 purchase totals =	$1,260.37		$1,372.1094	$1,372.11	$1,372.15	$1,372.10