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	$112.82	5.486%	$119.0093	$119.01	$119.00	$119.00
Purchase #2	$193.76	7.817%	$208.9062	$208.91	$208.90	$208.90
Purchase #3	$50.78	13.460%	$57.615	$57.62	$57.60	$57.60
Purchase #4	$83.95	13.733%	$95.4789	$95.48	$95.50	$95.50
Purchase #5	$243.37	13.235%	$275.58	$275.58	$275.60	$275.60
Purchase #6	$17.76	12.163%	$19.9201	$19.92	$19.90	$19.90
Purchase #7	$41.67	4.130%	$43.391	$43.39	$43.40	$43.40
7 purchase totals =	$744.11		$819.9005	$819.91	$819.90	$819.90