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	$31.29	3.476%	$32.3776	$32.38	$32.40	$32.40
Purchase #2	$173.43	12.681%	$195.4227	$195.42	$195.40	$195.40
Purchase #3	$107.41	4.157%	$111.875	$111.88	$111.90	$111.90
Purchase #4	$248.92	12.370%	$279.7114	$279.71	$279.70	$279.70
Purchase #5	$28.92	13.501%	$32.8245	$32.82	$32.80	$32.80
Purchase #6	$126.57	8.401%	$137.2031	$137.20	$137.20	$137.20
Purchase #7	$208.73	6.465%	$222.2244	$222.22	$222.20	$222.20
7 purchase totals =	$925.27		$1,011.6387	$1,011.63	$1,011.60	$1,011.60