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	$18.68	6.315%	$19.8596	$19.86	$19.85	$19.90
Purchase #2	$238.33	7.722%	$256.7338	$256.73	$256.75	$256.70
Purchase #3	$182.33	7.501%	$196.0066	$196.01	$196.00	$196.00
Purchase #4	$231.69	5.284%	$243.9325	$243.93	$243.95	$243.90
Purchase #5	$10.72	6.235%	$11.3884	$11.39	$11.40	$11.40
Purchase #6	$61.60	4.600%	$64.4336	$64.43	$64.45	$64.40
Purchase #7	$67.46	10.237%	$74.3659	$74.37	$74.35	$74.40
7 purchase totals =	$810.81		$866.7204	$866.72	$866.75	$866.70