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	$42.85	7.706%	$46.152	$46.15	$46.15	$46.20
Purchase #2	$59.56	10.468%	$65.7947	$65.79	$65.80	$65.80
Purchase #3	$172.63	13.143%	$195.3188	$195.32	$195.30	$195.30
Purchase #4	$240.51	6.741%	$256.7228	$256.72	$256.70	$256.70
Purchase #5	$180.75	13.824%	$205.7369	$205.74	$205.75	$205.70
Purchase #6	$76.79	9.212%	$83.8639	$83.86	$83.85	$83.90
Purchase #7	$213.27	7.786%	$229.8752	$229.88	$229.90	$229.90
7 purchase totals =	$986.36		$1,083.4643	$1,083.46	$1,083.45	$1,083.50