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	$196.53	13.272%	$222.6135	$222.61	$222.60	$222.60
Purchase #2	$144.26	10.321%	$159.1491	$159.15	$159.15	$159.10
Purchase #3	$65.31	6.117%	$69.305	$69.31	$69.30	$69.30
Purchase #4	$134.83	11.485%	$150.3152	$150.32	$150.30	$150.30
Purchase #5	$137.66	7.714%	$148.2791	$148.28	$148.30	$148.30
Purchase #6	$170.98	9.434%	$187.1103	$187.11	$187.10	$187.10
Purchase #7	$42.78	9.326%	$46.7697	$46.77	$46.75	$46.80
7 purchase totals =	$892.35		$983.5419	$983.55	$983.50	$983.50