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	$94.51	11.202%	$105.097	$105.10	$105.10	$105.10
Purchase #2	$91.73	8.768%	$99.7729	$99.77	$99.75	$99.80
Purchase #3	$137.93	3.564%	$142.8458	$142.85	$142.85	$142.80
Purchase #4	$147.34	7.355%	$158.1769	$158.18	$158.20	$158.20
Purchase #5	$70.67	6.568%	$75.3116	$75.31	$75.30	$75.30
Purchase #6	$131.57	10.573%	$145.4809	$145.48	$145.50	$145.50
Purchase #7	$160.50	4.425%	$167.6021	$167.60	$167.60	$167.60
7 purchase totals =	$834.25		$894.2872	$894.29	$894.30	$894.30