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	$74.46	11.193%	$82.7943	$82.79	$82.80	$82.80
Purchase #2	$101.85	4.410%	$106.3416	$106.34	$106.35	$106.30
Purchase #3	$119.91	6.105%	$127.2305	$127.23	$127.25	$127.20
Purchase #4	$127.97	9.510%	$140.1399	$140.14	$140.15	$140.10
Purchase #5	$55.40	6.392%	$58.9412	$58.94	$58.95	$58.90
Purchase #6	$160.71	5.281%	$169.1971	$169.20	$169.20	$169.20
Purchase #7	$231.74	10.255%	$255.5049	$255.50	$255.50	$255.50
7 purchase totals =	$872.04		$940.1495	$940.14	$940.20	$940.00