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	$233.39	9.503%	$255.5691	$255.57	$255.55	$255.60
Purchase #2	$242.36	13.363%	$274.7466	$274.75	$274.75	$274.70
Purchase #3	$91.53	9.460%	$100.1887	$100.19	$100.20	$100.20
Purchase #4	$244.33	4.342%	$254.9388	$254.94	$254.95	$254.90
Purchase #5	$175.26	11.525%	$195.4587	$195.46	$195.45	$195.50
Purchase #6	$45.56	10.587%	$50.3834	$50.38	$50.40	$50.40
Purchase #7	$83.63	5.393%	$88.1402	$88.14	$88.15	$88.10
7 purchase totals =	$1,116.06		$1,219.4255	$1,219.43	$1,219.45	$1,219.40