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	$154.78	8.511%	$167.9533	$167.95	$167.95	$168.00
Purchase #2	$157.96	9.342%	$172.7166	$172.72	$172.70	$172.70
Purchase #3	$131.50	11.437%	$146.5397	$146.54	$146.55	$146.50
Purchase #4	$44.65	13.804%	$50.8135	$50.81	$50.80	$50.80
Purchase #5	$173.25	12.788%	$195.4052	$195.41	$195.40	$195.40
Purchase #6	$144.29	3.531%	$149.3849	$149.38	$149.40	$149.40
Purchase #7	$102.85	8.504%	$111.5964	$111.60	$111.60	$111.60
7 purchase totals =	$909.28		$994.4096	$994.41	$994.40	$994.40