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	$204.79	8.130%	$221.4394	$221.44	$221.45	$221.40
Purchase #2	$247.34	10.269%	$272.7393	$272.74	$272.75	$272.70
Purchase #3	$102.87	8.554%	$111.6695	$111.67	$111.65	$111.70
Purchase #4	$243.34	13.216%	$275.4998	$275.50	$275.50	$275.50
Purchase #5	$91.69	8.739%	$99.7028	$99.70	$99.70	$99.70
Purchase #6	$172.33	3.810%	$178.8958	$178.90	$178.90	$178.90
Purchase #7	$142.68	8.293%	$154.5125	$154.51	$154.50	$154.50
7 purchase totals =	$1,205.04		$1,314.4591	$1,314.46	$1,314.45	$1,314.40