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	$200.96	10.686%	$222.4346	$222.43	$222.45	$222.40
Purchase #2	$206.50	11.124%	$229.4711	$229.47	$229.45	$229.50
Purchase #3	$193.66	12.603%	$218.067	$218.07	$218.05	$218.10
Purchase #4	$199.72	4.788%	$209.2826	$209.28	$209.30	$209.30
Purchase #5	$81.49	12.294%	$91.5084	$91.51	$91.50	$91.50
Purchase #6	$167.51	4.594%	$175.2054	$175.21	$175.20	$175.20
Purchase #7	$46.93	13.827%	$53.419	$53.42	$53.40	$53.40
7 purchase totals =	$1,096.77		$1,199.3881	$1,199.39	$1,199.35	$1,199.40