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	$214.91	6.283%	$228.4128	$228.41	$228.40	$228.40
Purchase #2	$49.89	8.565%	$54.1631	$54.16	$54.15	$54.20
Purchase #3	$177.53	10.698%	$196.5222	$196.52	$196.50	$196.50
Purchase #4	$231.31	6.628%	$246.6412	$246.64	$246.65	$246.60
Purchase #5	$29.57	9.362%	$32.3383	$32.34	$32.35	$32.30
Purchase #6	$142.85	5.605%	$150.8567	$150.86	$150.85	$150.90
Purchase #7	$222.51	6.619%	$237.2379	$237.24	$237.25	$237.20
7 purchase totals =	$1,068.57		$1,146.1722	$1,146.17	$1,146.15	$1,146.10