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	$90.34	12.293%	$101.4455	$101.45	$101.45	$101.40
Purchase #2	$38.90	6.781%	$41.5378	$41.54	$41.55	$41.50
Purchase #3	$6.47	8.542%	$7.0227	$7.02	$7.00	$7.00
Purchase #4	$223.47	6.164%	$237.2447	$237.24	$237.25	$237.20
Purchase #5	$161.46	6.626%	$172.1583	$172.16	$172.15	$172.20
Purchase #6	$231.59	5.153%	$243.5238	$243.52	$243.50	$243.50
Purchase #7	$92.79	13.663%	$105.4679	$105.47	$105.45	$105.50
7 purchase totals =	$845.02		$908.4007	$908.40	$908.35	$908.30