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	$40.35	13.145%	$45.654	$45.65	$45.65	$45.70
Purchase #2	$227.28	12.500%	$255.69	$255.69	$255.70	$255.70
Purchase #3	$16.61	10.139%	$18.2941	$18.29	$18.30	$18.30
Purchase #4	$42.66	12.728%	$48.0898	$48.09	$48.10	$48.10
Purchase #5	$229.82	6.277%	$244.2458	$244.25	$244.25	$244.20
Purchase #6	$12.37	7.872%	$13.3438	$13.34	$13.35	$13.30
Purchase #7	$112.33	5.658%	$118.6856	$118.69	$118.70	$118.70
7 purchase totals =	$681.42		$744.0031	$744.00	$744.05	$744.00