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	$135.65	11.226%	$150.8781	$150.88	$150.90	$150.90
Purchase #2	$55.63	12.747%	$62.7212	$62.72	$62.70	$62.70
Purchase #3	$105.87	9.857%	$116.3056	$116.31	$116.30	$116.30
Purchase #4	$232.80	8.472%	$252.5228	$252.52	$252.50	$252.50
Purchase #5	$245.85	6.526%	$261.8942	$261.89	$261.90	$261.90
Purchase #6	$138.86	9.654%	$152.2655	$152.27	$152.25	$152.30
Purchase #7	$33.35	3.840%	$34.6306	$34.63	$34.65	$34.60
7 purchase totals =	$948.01		$1,031.2180	$1,031.22	$1,031.20	$1,031.20