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	$146.90	3.430%	$151.9387	$151.94	$151.95	$151.90
Purchase #2	$69.61	12.771%	$78.4999	$78.50	$78.50	$78.50
Purchase #3	$64.39	4.821%	$67.4942	$67.49	$67.50	$67.50
Purchase #4	$125.54	12.165%	$140.8119	$140.81	$140.80	$140.80
Purchase #5	$202.78	13.589%	$230.3358	$230.34	$230.35	$230.30
Purchase #6	$92.83	10.130%	$102.2337	$102.23	$102.25	$102.20
Purchase #7	$149.76	6.666%	$159.743	$159.74	$159.75	$159.70
7 purchase totals =	$851.81		$931.0572	$931.05	$931.10	$930.90