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	$113.55	12.103%	$127.293	$127.29	$127.30	$127.30
Purchase #2	$131.96	11.576%	$147.2357	$147.24	$147.25	$147.20
Purchase #3	$221.34	6.576%	$235.8953	$235.90	$235.90	$235.90
Purchase #4	$130.65	12.343%	$146.7761	$146.78	$146.80	$146.80
Purchase #5	$50.60	12.102%	$56.7236	$56.72	$56.70	$56.70
Purchase #6	$115.67	10.113%	$127.3677	$127.37	$127.35	$127.40
Purchase #7	$6.74	7.327%	$7.2338	$7.23	$7.25	$7.20
7 purchase totals =	$770.51		$848.5252	$848.53	$848.55	$848.50