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	$155.70	12.606%	$175.3275	$175.33	$175.35	$175.30
Purchase #2	$185.90	5.664%	$196.4294	$196.43	$196.45	$196.40
Purchase #3	$176.47	13.828%	$200.8723	$200.87	$200.85	$200.90
Purchase #4	$45.77	6.708%	$48.8403	$48.84	$48.85	$48.80
Purchase #5	$107.81	4.572%	$112.7391	$112.74	$112.75	$112.70
Purchase #6	$7.61	12.624%	$8.5707	$8.57	$8.55	$8.60
Purchase #7	$11.28	8.303%	$12.2166	$12.22	$12.20	$12.20
7 purchase totals =	$690.54		$754.9959	$755.00	$755.00	$754.90