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	$39.69	10.634%	$43.9106	$43.91	$43.90	$43.90
Purchase #2	$84.51	4.339%	$88.1769	$88.18	$88.20	$88.20
Purchase #3	$11.44	8.549%	$12.418	$12.42	$12.40	$12.40
Purchase #4	$152.97	11.322%	$170.2893	$170.29	$170.30	$170.30
Purchase #5	$79.30	5.187%	$83.4133	$83.41	$83.40	$83.40
Purchase #6	$38.53	13.260%	$43.6391	$43.64	$43.65	$43.60
Purchase #7	$105.90	12.643%	$119.2889	$119.29	$119.30	$119.30
7 purchase totals =	$512.34		$561.1361	$561.14	$561.15	$561.10