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	$45.85	5.332%	$48.2947	$48.29	$48.30	$48.30
Purchase #2	$246.86	3.657%	$255.8877	$255.89	$255.90	$255.90
Purchase #3	$145.30	3.487%	$150.3666	$150.37	$150.35	$150.40
Purchase #4	$247.64	12.836%	$279.4271	$279.43	$279.45	$279.40
Purchase #5	$103.52	6.554%	$110.3047	$110.30	$110.30	$110.30
Purchase #6	$238.67	10.388%	$263.463	$263.46	$263.45	$263.50
Purchase #7	$235.50	11.532%	$262.6579	$262.66	$262.65	$262.70
7 purchase totals =	$1,263.34		$1,370.4017	$1,370.40	$1,370.40	$1,370.50