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	$107.93	8.601%	$117.2131	$117.21	$117.20	$117.20
Purchase #2	$78.96	8.216%	$85.4474	$85.45	$85.45	$85.40
Purchase #3	$120.72	5.311%	$127.1314	$127.13	$127.15	$127.10
Purchase #4	$124.49	3.172%	$128.4388	$128.44	$128.45	$128.40
Purchase #5	$97.58	3.632%	$101.1241	$101.12	$101.10	$101.10
Purchase #6	$108.51	7.226%	$116.3509	$116.35	$116.35	$116.40
Purchase #7	$175.40	5.858%	$185.6749	$185.67	$185.65	$185.70
7 purchase totals =	$813.59		$861.3806	$861.37	$861.35	$861.30