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	$85.53	8.401%	$92.7154	$92.72	$92.70	$92.70
Purchase #2	$38.99	11.157%	$43.3401	$43.34	$43.35	$43.30
Purchase #3	$230.57	8.482%	$250.1269	$250.13	$250.15	$250.10
Purchase #4	$121.37	13.276%	$137.4831	$137.48	$137.50	$137.50
Purchase #5	$164.29	5.534%	$173.3818	$173.38	$173.40	$173.40
Purchase #6	$227.60	9.748%	$249.7864	$249.79	$249.80	$249.80
Purchase #7	$69.66	13.169%	$78.8335	$78.83	$78.85	$78.80
7 purchase totals =	$938.01		$1,025.6672	$1,025.67	$1,025.75	$1,025.60