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	$47.50	9.480%	$52.003	$52.00	$52.00	$52.00
Purchase #2	$99.76	6.203%	$105.9481	$105.95	$105.95	$105.90
Purchase #3	$49.87	5.745%	$52.735	$52.74	$52.75	$52.70
Purchase #4	$116.47	8.868%	$126.7986	$126.80	$126.80	$126.80
Purchase #5	$123.31	7.180%	$132.1637	$132.16	$132.15	$132.20
Purchase #6	$140.47	4.321%	$146.5397	$146.54	$146.55	$146.50
Purchase #7	$36.66	5.331%	$38.6143	$38.61	$38.60	$38.60
7 purchase totals =	$614.04		$654.8024	$654.80	$654.80	$654.70