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	$36.76	3.183%	$37.9301	$37.93	$37.95	$37.90
Purchase #2	$237.71	7.594%	$255.7617	$255.76	$255.75	$255.80
Purchase #3	$173.45	10.861%	$192.2884	$192.29	$192.30	$192.30
Purchase #4	$84.96	3.835%	$88.2182	$88.22	$88.20	$88.20
Purchase #5	$198.85	5.689%	$210.1626	$210.16	$210.15	$210.20
Purchase #6	$188.34	11.385%	$209.7825	$209.78	$209.80	$209.80
Purchase #7	$169.85	9.175%	$185.4337	$185.43	$185.45	$185.40
7 purchase totals =	$1,089.92		$1,179.5772	$1,179.57	$1,179.60	$1,179.60