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	$126.94	4.282%	$132.3756	$132.38	$132.40	$132.40
Purchase #2	$249.56	6.324%	$265.3422	$265.34	$265.35	$265.30
Purchase #3	$150.61	12.309%	$169.1486	$169.15	$169.15	$169.10
Purchase #4	$37.65	10.441%	$41.581	$41.58	$41.60	$41.60
Purchase #5	$49.80	12.729%	$56.139	$56.14	$56.15	$56.10
Purchase #6	$195.85	5.623%	$206.8626	$206.86	$206.85	$206.90
Purchase #7	$56.33	5.660%	$59.5183	$59.52	$59.50	$59.50
7 purchase totals =	$866.74		$930.9673	$930.97	$931.00	$930.90