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	$103.69	12.684%	$116.842	$116.84	$116.85	$116.80
Purchase #2	$159.97	7.818%	$172.4765	$172.48	$172.50	$172.50
Purchase #3	$240.34	6.599%	$256.2	$256.20	$256.20	$256.20
Purchase #4	$216.85	11.606%	$242.0176	$242.02	$242.00	$242.00
Purchase #5	$19.72	10.869%	$21.8634	$21.86	$21.85	$21.90
Purchase #6	$149.31	6.272%	$158.6747	$158.67	$158.65	$158.70
Purchase #7	$123.83	11.682%	$138.2958	$138.30	$138.30	$138.30
7 purchase totals =	$1,013.71		$1,106.3700	$1,106.37	$1,106.35	$1,106.40