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	$222.75	11.282%	$247.8807	$247.88	$247.90	$247.90
Purchase #2	$86.47	13.836%	$98.434	$98.43	$98.45	$98.40
Purchase #3	$75.39	10.742%	$83.4884	$83.49	$83.50	$83.50
Purchase #4	$170.80	10.479%	$188.6981	$188.70	$188.70	$188.70
Purchase #5	$116.99	5.869%	$123.8561	$123.86	$123.85	$123.90
Purchase #6	$108.49	8.155%	$117.3374	$117.34	$117.35	$117.30
Purchase #7	$170.30	12.223%	$191.1158	$191.12	$191.10	$191.10
7 purchase totals =	$951.19		$1,050.8105	$1,050.82	$1,050.85	$1,050.80