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	$42.54	13.196%	$48.1536	$48.15	$48.15	$48.20
Purchase #2	$221.59	12.452%	$249.1824	$249.18	$249.20	$249.20
Purchase #3	$152.54	8.455%	$165.4373	$165.44	$165.45	$165.40
Purchase #4	$230.60	13.793%	$262.4067	$262.41	$262.40	$262.40
Purchase #5	$238.50	8.250%	$258.1763	$258.18	$258.20	$258.20
Purchase #6	$45.70	11.303%	$50.8655	$50.87	$50.85	$50.90
Purchase #7	$47.25	11.465%	$52.6672	$52.67	$52.65	$52.70
7 purchase totals =	$978.72		$1,086.8890	$1,086.90	$1,086.90	$1,087.00