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	$44.69	3.756%	$46.3686	$46.37	$46.35	$46.40
Purchase #2	$146.45	10.715%	$162.1421	$162.14	$162.15	$162.10
Purchase #3	$22.56	10.288%	$24.881	$24.88	$24.90	$24.90
Purchase #4	$222.48	3.531%	$230.3358	$230.34	$230.35	$230.30
Purchase #5	$230.58	6.269%	$245.0351	$245.04	$245.05	$245.00
Purchase #6	$63.66	13.103%	$72.0014	$72.00	$72.00	$72.00
Purchase #7	$139.53	8.305%	$151.118	$151.12	$151.10	$151.10
7 purchase totals =	$869.95		$931.8820	$931.89	$931.90	$931.80