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	$159.40	4.468%	$166.522	$166.52	$166.50	$166.50
Purchase #2	$22.35	8.211%	$24.1852	$24.19	$24.20	$24.20
Purchase #3	$245.63	9.724%	$269.5151	$269.52	$269.50	$269.50
Purchase #4	$89.47	10.837%	$99.1659	$99.17	$99.15	$99.20
Purchase #5	$57.52	12.806%	$64.886	$64.89	$64.90	$64.90
Purchase #6	$192.67	6.176%	$204.5693	$204.57	$204.55	$204.60
Purchase #7	$230.72	6.106%	$244.8078	$244.81	$244.80	$244.80
7 purchase totals =	$997.76		$1,073.6513	$1,073.67	$1,073.60	$1,073.70