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	$113.54	8.712%	$123.4316	$123.43	$123.45	$123.40
Purchase #2	$116.55	9.652%	$127.7994	$127.80	$127.80	$127.80
Purchase #3	$137.42	8.680%	$149.3481	$149.35	$149.35	$149.30
Purchase #4	$143.79	5.489%	$151.6826	$151.68	$151.70	$151.70
Purchase #5	$40.50	7.574%	$43.5675	$43.57	$43.55	$43.60
Purchase #6	$247.89	12.832%	$279.6992	$279.70	$279.70	$279.70
Purchase #7	$125.33	6.403%	$133.3549	$133.35	$133.35	$133.40
7 purchase totals =	$925.02		$1,008.8833	$1,008.88	$1,008.90	$1,008.90