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	$148.69	8.214%	$160.9034	$160.90	$160.90	$160.90
Purchase #2	$223.66	4.183%	$233.0157	$233.02	$233.00	$233.00
Purchase #3	$244.68	13.746%	$278.3137	$278.31	$278.30	$278.30
Purchase #4	$179.59	6.848%	$191.8883	$191.89	$191.90	$191.90
Purchase #5	$183.47	13.862%	$208.9026	$208.90	$208.90	$208.90
Purchase #6	$105.93	9.753%	$116.2614	$116.26	$116.25	$116.30
Purchase #7	$200.65	12.233%	$225.1955	$225.20	$225.20	$225.20
7 purchase totals =	$1,286.67		$1,414.4806	$1,414.48	$1,414.45	$1,414.50