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	$164.62	5.626%	$173.8815	$173.88	$173.90	$173.90
Purchase #2	$160.40	6.497%	$170.8212	$170.82	$170.80	$170.80
Purchase #3	$91.91	13.106%	$103.9557	$103.96	$103.95	$104.00
Purchase #4	$158.25	5.850%	$167.5076	$167.51	$167.50	$167.50
Purchase #5	$155.40	11.534%	$173.3238	$173.32	$173.30	$173.30
Purchase #6	$30.31	11.222%	$33.7114	$33.71	$33.70	$33.70
Purchase #7	$68.70	6.149%	$72.9244	$72.92	$72.90	$72.90
7 purchase totals =	$829.59		$896.1256	$896.12	$896.05	$896.10