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	$172.80	13.672%	$196.4252	$196.43	$196.45	$196.40
Purchase #2	$112.67	8.792%	$122.5759	$122.58	$122.60	$122.60
Purchase #3	$22.60	11.713%	$25.2471	$25.25	$25.25	$25.20
Purchase #4	$80.88	12.478%	$90.9722	$90.97	$90.95	$91.00
Purchase #5	$155.38	5.817%	$164.4185	$164.42	$164.40	$164.40
Purchase #6	$170.60	4.153%	$177.685	$177.69	$177.70	$177.70
Purchase #7	$119.52	6.172%	$126.8968	$126.90	$126.90	$126.90
7 purchase totals =	$834.45		$904.2207	$904.24	$904.25	$904.20