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	$38.39	12.237%	$43.0878	$43.09	$43.10	$43.10
Purchase #2	$213.79	7.436%	$229.6874	$229.69	$229.70	$229.70
Purchase #3	$148.30	7.312%	$159.1437	$159.14	$159.15	$159.10
Purchase #4	$241.62	4.449%	$252.3697	$252.37	$252.35	$252.40
Purchase #5	$132.62	5.816%	$140.3332	$140.33	$140.35	$140.30
Purchase #6	$12.46	13.238%	$14.1095	$14.11	$14.10	$14.10
Purchase #7	$215.96	3.327%	$223.145	$223.15	$223.15	$223.10
7 purchase totals =	$1,003.14		$1,061.8763	$1,061.88	$1,061.90	$1,061.80