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	$98.93	13.426%	$112.2123	$112.21	$112.20	$112.20
Purchase #2	$12.49	4.733%	$13.0812	$13.08	$13.10	$13.10
Purchase #3	$112.36	9.780%	$123.3488	$123.35	$123.35	$123.30
Purchase #4	$235.33	4.367%	$245.6069	$245.61	$245.60	$245.60
Purchase #5	$61.85	9.629%	$67.8055	$67.81	$67.80	$67.80
Purchase #6	$203.25	13.411%	$230.5079	$230.51	$230.50	$230.50
Purchase #7	$67.38	13.263%	$76.3166	$76.32	$76.30	$76.30
7 purchase totals =	$791.59		$868.8792	$868.89	$868.85	$868.80