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	$188.37	12.616%	$212.1348	$212.13	$212.15	$212.10
Purchase #2	$132.97	8.195%	$143.8669	$143.87	$143.85	$143.90
Purchase #3	$178.57	7.474%	$191.9163	$191.92	$191.90	$191.90
Purchase #4	$55.58	6.540%	$59.2149	$59.21	$59.20	$59.20
Purchase #5	$184.34	8.144%	$199.3526	$199.35	$199.35	$199.40
Purchase #6	$161.56	6.519%	$172.0921	$172.09	$172.10	$172.10
Purchase #7	$218.77	11.760%	$244.4974	$244.50	$244.50	$244.50
7 purchase totals =	$1,120.16		$1,223.0750	$1,223.07	$1,223.05	$1,223.10