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	$198.95	8.301%	$215.4648	$215.46	$215.45	$215.50
Purchase #2	$191.25	7.760%	$206.091	$206.09	$206.10	$206.10
Purchase #3	$136.91	13.578%	$155.4996	$155.50	$155.50	$155.50
Purchase #4	$6.89	4.155%	$7.1763	$7.18	$7.20	$7.20
Purchase #5	$10.98	13.838%	$12.4994	$12.50	$12.50	$12.50
Purchase #6	$218.54	5.738%	$231.0798	$231.08	$231.10	$231.10
Purchase #7	$41.96	13.596%	$47.6649	$47.66	$47.65	$47.70
7 purchase totals =	$805.48		$875.4758	$875.47	$875.50	$875.60