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	$249.89	4.131%	$260.213	$260.21	$260.20	$260.20
Purchase #2	$93.84	13.571%	$106.575	$106.58	$106.60	$106.60
Purchase #3	$119.94	9.741%	$131.6234	$131.62	$131.60	$131.60
Purchase #4	$230.62	9.227%	$251.8993	$251.90	$251.90	$251.90
Purchase #5	$153.66	9.297%	$167.9458	$167.95	$167.95	$167.90
Purchase #6	$166.73	13.293%	$188.8934	$188.89	$188.90	$188.90
Purchase #7	$39.75	9.635%	$43.5799	$43.58	$43.60	$43.60
7 purchase totals =	$1,054.43		$1,150.7298	$1,150.73	$1,150.75	$1,150.70