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	$171.43	12.167%	$192.2879	$192.29	$192.30	$192.30
Purchase #2	$242.43	12.140%	$271.861	$271.86	$271.85	$271.90
Purchase #3	$66.54	13.646%	$75.62	$75.62	$75.60	$75.60
Purchase #4	$74.90	10.776%	$82.9712	$82.97	$82.95	$83.00
Purchase #5	$98.45	5.549%	$103.913	$103.91	$103.90	$103.90
Purchase #6	$98.75	7.317%	$105.9755	$105.98	$106.00	$106.00
Purchase #7	$158.99	8.393%	$172.334	$172.33	$172.35	$172.30
7 purchase totals =	$911.49		$1,004.9626	$1,004.96	$1,004.95	$1,005.00