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	$7.37	6.792%	$7.8706	$7.87	$7.85	$7.90
Purchase #2	$13.30	10.141%	$14.6488	$14.65	$14.65	$14.60
Purchase #3	$76.63	13.692%	$87.1222	$87.12	$87.10	$87.10
Purchase #4	$29.81	6.580%	$31.7715	$31.77	$31.75	$31.80
Purchase #5	$147.85	12.779%	$166.7438	$166.74	$166.75	$166.70
Purchase #6	$155.30	11.133%	$172.5895	$172.59	$172.60	$172.60
Purchase #7	$178.33	12.197%	$200.0809	$200.08	$200.10	$200.10
7 purchase totals =	$608.59		$680.8273	$680.82	$680.80	$680.80