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	$217.55	6.229%	$231.1012	$231.10	$231.10	$231.10
Purchase #2	$67.29	6.671%	$71.7789	$71.78	$71.80	$71.80
Purchase #3	$224.71	10.375%	$248.0237	$248.02	$248.00	$248.00
Purchase #4	$15.84	13.642%	$18.0009	$18.00	$18.00	$18.00
Purchase #5	$117.38	5.183%	$123.4638	$123.46	$123.45	$123.50
Purchase #6	$9.91	4.797%	$10.3854	$10.39	$10.40	$10.40
Purchase #7	$144.31	5.433%	$152.1504	$152.15	$152.15	$152.20
7 purchase totals =	$796.99		$854.9043	$854.90	$854.90	$855.00