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	$57.43	4.811%	$60.193	$60.19	$60.20	$60.20
Purchase #2	$116.89	8.497%	$126.8221	$126.82	$126.80	$126.80
Purchase #3	$161.66	3.829%	$167.85	$167.85	$167.85	$167.90
Purchase #4	$130.39	9.315%	$142.5358	$142.54	$142.55	$142.50
Purchase #5	$134.96	8.758%	$146.7798	$146.78	$146.80	$146.80
Purchase #6	$163.72	5.468%	$172.6722	$172.67	$172.65	$172.70
Purchase #7	$230.57	8.369%	$249.8664	$249.87	$249.85	$249.90
7 purchase totals =	$995.62		$1,066.7193	$1,066.72	$1,066.70	$1,066.80