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	$145.34	12.741%	$163.8578	$163.86	$163.85	$163.90
Purchase #2	$95.49	8.736%	$103.832	$103.83	$103.85	$103.80
Purchase #3	$246.36	6.124%	$261.4471	$261.45	$261.45	$261.40
Purchase #4	$211.98	8.312%	$229.5998	$229.60	$229.60	$229.60
Purchase #5	$83.37	8.377%	$90.3539	$90.35	$90.35	$90.40
Purchase #6	$199.83	9.167%	$218.1484	$218.15	$218.15	$218.10
Purchase #7	$140.73	7.846%	$151.7717	$151.77	$151.75	$151.80
7 purchase totals =	$1,123.10		$1,219.0107	$1,219.01	$1,219.00	$1,219.00