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	$85.63	11.852%	$95.7789	$95.78	$95.80	$95.80
Purchase #2	$142.26	6.363%	$151.312	$151.31	$151.30	$151.30
Purchase #3	$108.48	5.872%	$114.8499	$114.85	$114.85	$114.80
Purchase #4	$24.83	13.431%	$28.1649	$28.16	$28.15	$28.20
Purchase #5	$58.71	6.528%	$62.5426	$62.54	$62.55	$62.50
Purchase #6	$46.94	8.196%	$50.7872	$50.79	$50.80	$50.80
Purchase #7	$12.40	6.847%	$13.249	$13.25	$13.25	$13.20
7 purchase totals =	$479.25		$516.6845	$516.68	$516.70	$516.60