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	$220.40	6.698%	$235.1624	$235.16	$235.15	$235.20
Purchase #2	$81.96	10.426%	$90.5051	$90.51	$90.50	$90.50
Purchase #3	$66.72	4.352%	$69.6237	$69.62	$69.60	$69.60
Purchase #4	$194.91	11.344%	$217.0206	$217.02	$217.00	$217.00
Purchase #5	$208.56	13.112%	$235.9064	$235.91	$235.90	$235.90
Purchase #6	$161.72	8.591%	$175.6134	$175.61	$175.60	$175.60
Purchase #7	$122.41	8.254%	$132.5137	$132.51	$132.50	$132.50
7 purchase totals =	$1,056.68		$1,156.3453	$1,156.34	$1,156.25	$1,156.30