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	$194.93	7.492%	$209.5342	$209.53	$209.55	$209.50
Purchase #2	$231.53	6.732%	$247.1166	$247.12	$247.10	$247.10
Purchase #3	$158.63	9.310%	$173.3985	$173.40	$173.40	$173.40
Purchase #4	$19.79	6.160%	$21.0091	$21.01	$21.00	$21.00
Purchase #5	$22.71	11.111%	$25.2333	$25.23	$25.25	$25.20
Purchase #6	$44.34	3.294%	$45.8006	$45.80	$45.80	$45.80
Purchase #7	$83.64	8.161%	$90.4659	$90.47	$90.45	$90.50
7 purchase totals =	$755.57		$812.5582	$812.56	$812.55	$812.50