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	$139.95	4.810%	$146.6816	$146.68	$146.70	$146.70
Purchase #2	$100.69	4.849%	$105.5725	$105.57	$105.55	$105.60
Purchase #3	$230.94	9.760%	$253.4797	$253.48	$253.50	$253.50
Purchase #4	$46.59	11.470%	$51.9339	$51.93	$51.95	$51.90
Purchase #5	$250.51	13.736%	$284.9201	$284.92	$284.90	$284.90
Purchase #6	$9.72	12.231%	$10.9089	$10.91	$10.90	$10.90
Purchase #7	$173.49	8.623%	$188.45	$188.45	$188.45	$188.50
7 purchase totals =	$951.89		$1,041.9467	$1,041.94	$1,041.95	$1,042.00