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	$137.28	5.316%	$144.5778	$144.58	$144.60	$144.60
Purchase #2	$179.25	12.193%	$201.106	$201.11	$201.10	$201.10
Purchase #3	$93.27	5.447%	$98.3504	$98.35	$98.35	$98.40
Purchase #4	$42.43	7.629%	$45.667	$45.67	$45.65	$45.70
Purchase #5	$214.39	4.333%	$223.6795	$223.68	$223.70	$223.70
Purchase #6	$223.25	4.738%	$233.8276	$233.83	$233.85	$233.80
Purchase #7	$69.28	12.588%	$78.001	$78.00	$78.00	$78.00
7 purchase totals =	$959.15		$1,025.2093	$1,025.22	$1,025.25	$1,025.30