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	$157.62	9.335%	$172.3338	$172.33	$172.35	$172.30
Purchase #2	$95.34	4.238%	$99.3805	$99.38	$99.40	$99.40
Purchase #3	$185.49	13.823%	$211.1303	$211.13	$211.15	$211.10
Purchase #4	$136.30	5.145%	$143.3126	$143.31	$143.30	$143.30
Purchase #5	$218.47	11.566%	$243.7382	$243.74	$243.75	$243.70
Purchase #6	$71.49	12.709%	$80.5757	$80.58	$80.60	$80.60
Purchase #7	$66.85	7.461%	$71.8377	$71.84	$71.85	$71.80
7 purchase totals =	$931.56		$1,022.3088	$1,022.31	$1,022.40	$1,022.20