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	$96.35	10.248%	$106.2239	$106.22	$106.20	$106.20
Purchase #2	$155.26	9.125%	$169.4275	$169.43	$169.45	$169.40
Purchase #3	$117.71	8.687%	$127.9355	$127.94	$127.95	$127.90
Purchase #4	$73.44	7.446%	$78.9083	$78.91	$78.90	$78.90
Purchase #5	$233.94	3.668%	$242.5209	$242.52	$242.50	$242.50
Purchase #6	$152.42	13.704%	$173.3076	$173.31	$173.30	$173.30
Purchase #7	$37.84	3.770%	$39.2666	$39.27	$39.25	$39.30
7 purchase totals =	$866.96		$937.5903	$937.60	$937.55	$937.50