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	$126.83	7.344%	$136.1444	$136.14	$136.15	$136.10
Purchase #2	$189.61	3.338%	$195.9392	$195.94	$195.95	$195.90
Purchase #3	$54.72	8.435%	$59.3356	$59.34	$59.35	$59.30
Purchase #4	$141.96	11.458%	$158.2258	$158.23	$158.25	$158.20
Purchase #5	$210.94	13.197%	$238.7778	$238.78	$238.80	$238.80
Purchase #6	$236.29	7.589%	$254.222	$254.22	$254.20	$254.20
Purchase #7	$101.55	9.536%	$111.2338	$111.23	$111.25	$111.20
7 purchase totals =	$1,061.90		$1,153.8786	$1,153.88	$1,153.95	$1,153.70