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	$55.79	3.717%	$57.8637	$57.86	$57.85	$57.90
Purchase #2	$136.80	8.548%	$148.4937	$148.49	$148.50	$148.50
Purchase #3	$42.65	7.679%	$45.9251	$45.93	$45.95	$45.90
Purchase #4	$204.67	8.633%	$222.3392	$222.34	$222.35	$222.30
Purchase #5	$58.91	12.525%	$66.2885	$66.29	$66.30	$66.30
Purchase #6	$112.57	3.295%	$116.2792	$116.28	$116.30	$116.30
Purchase #7	$151.63	11.205%	$168.6201	$168.62	$168.60	$168.60
7 purchase totals =	$763.02		$825.8095	$825.81	$825.85	$825.80