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	$141.89	12.388%	$159.4673	$159.47	$159.45	$159.50
Purchase #2	$133.69	13.334%	$151.5162	$151.52	$151.50	$151.50
Purchase #3	$247.53	8.482%	$268.5255	$268.53	$268.55	$268.50
Purchase #4	$95.62	9.816%	$105.0061	$105.01	$105.00	$105.00
Purchase #5	$220.30	4.264%	$229.6936	$229.69	$229.70	$229.70
Purchase #6	$50.53	10.552%	$55.8619	$55.86	$55.85	$55.90
Purchase #7	$54.67	13.224%	$61.8996	$61.90	$61.90	$61.90
7 purchase totals =	$944.23		$1,031.9702	$1,031.98	$1,031.95	$1,032.00