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	$123.42	5.690%	$130.4426	$130.44	$130.45	$130.40
Purchase #2	$31.35	3.754%	$32.5269	$32.53	$32.55	$32.50
Purchase #3	$40.92	7.843%	$44.1294	$44.13	$44.15	$44.10
Purchase #4	$145.66	13.630%	$165.5135	$165.51	$165.50	$165.50
Purchase #5	$43.91	10.836%	$48.6681	$48.67	$48.65	$48.70
Purchase #6	$64.50	12.872%	$72.8024	$72.80	$72.80	$72.80
Purchase #7	$25.87	4.431%	$27.0163	$27.02	$27.00	$27.00
7 purchase totals =	$475.63		$521.0992	$521.10	$521.10	$521.00