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	$67.68	8.547%	$73.4646	$73.46	$73.45	$73.50
Purchase #2	$242.54	13.262%	$274.7057	$274.71	$274.70	$274.70
Purchase #3	$219.61	11.470%	$244.7993	$244.80	$244.80	$244.80
Purchase #4	$167.31	7.507%	$179.87	$179.87	$179.85	$179.90
Purchase #5	$68.36	4.566%	$71.4813	$71.48	$71.50	$71.50
Purchase #6	$87.39	3.634%	$90.5658	$90.57	$90.55	$90.60
Purchase #7	$157.57	4.853%	$165.2169	$165.22	$165.20	$165.20
7 purchase totals =	$1,010.46		$1,100.1036	$1,100.11	$1,100.05	$1,100.20