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	$101.63	4.539%	$106.243	$106.24	$106.25	$106.20
Purchase #2	$216.72	8.825%	$235.8455	$235.85	$235.85	$235.80
Purchase #3	$140.30	7.733%	$151.1494	$151.15	$151.15	$151.10
Purchase #4	$109.25	10.285%	$120.4864	$120.49	$120.50	$120.50
Purchase #5	$133.72	6.122%	$141.9063	$141.91	$141.90	$141.90
Purchase #6	$242.31	13.558%	$275.1624	$275.16	$275.15	$275.20
Purchase #7	$99.95	3.737%	$103.6851	$103.69	$103.70	$103.70
7 purchase totals =	$1,043.88		$1,134.4781	$1,134.49	$1,134.50	$1,134.40