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	$83.33	8.317%	$90.2606	$90.26	$90.25	$90.30
Purchase #2	$222.33	11.503%	$247.9046	$247.90	$247.90	$247.90
Purchase #3	$65.74	7.348%	$70.5706	$70.57	$70.55	$70.60
Purchase #4	$246.71	8.173%	$266.8736	$266.87	$266.85	$266.90
Purchase #5	$130.93	5.150%	$137.6729	$137.67	$137.65	$137.70
Purchase #6	$146.78	9.227%	$160.3234	$160.32	$160.30	$160.30
Purchase #7	$52.52	9.366%	$57.439	$57.44	$57.45	$57.40
7 purchase totals =	$948.34		$1,031.0447	$1,031.03	$1,030.95	$1,031.10