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	$149.37	6.810%	$159.5421	$159.54	$159.55	$159.50
Purchase #2	$222.44	4.159%	$231.6913	$231.69	$231.70	$231.70
Purchase #3	$166.50	13.308%	$188.6578	$188.66	$188.65	$188.70
Purchase #4	$40.72	4.873%	$42.7043	$42.70	$42.70	$42.70
Purchase #5	$93.35	4.206%	$97.2763	$97.28	$97.30	$97.30
Purchase #6	$185.33	11.589%	$206.8079	$206.81	$206.80	$206.80
Purchase #7	$147.30	9.229%	$160.8943	$160.89	$160.90	$160.90
7 purchase totals =	$1,005.01		$1,087.5740	$1,087.57	$1,087.60	$1,087.60