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	$40.30	7.828%	$43.4547	$43.45	$43.45	$43.50
Purchase #2	$85.89	7.300%	$92.16	$92.16	$92.15	$92.20
Purchase #3	$240.37	4.537%	$251.2756	$251.28	$251.30	$251.30
Purchase #4	$62.62	13.621%	$71.1495	$71.15	$71.15	$71.10
Purchase #5	$63.43	5.184%	$66.7182	$66.72	$66.70	$66.70
Purchase #6	$35.86	8.219%	$38.8073	$38.81	$38.80	$38.80
Purchase #7	$241.61	8.603%	$262.3957	$262.40	$262.40	$262.40
7 purchase totals =	$770.08		$825.9610	$825.97	$825.95	$826.00