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	$123.88	7.219%	$132.8229	$132.82	$132.80	$132.80
Purchase #2	$66.39	10.492%	$73.3556	$73.36	$73.35	$73.40
Purchase #3	$54.34	5.716%	$57.4461	$57.45	$57.45	$57.40
Purchase #4	$92.54	7.709%	$99.6739	$99.67	$99.65	$99.70
Purchase #5	$109.34	7.655%	$117.71	$117.71	$117.70	$117.70
Purchase #6	$69.94	5.482%	$73.7741	$73.77	$73.75	$73.80
Purchase #7	$52.31	4.219%	$54.517	$54.52	$54.50	$54.50
7 purchase totals =	$568.74		$609.2996	$609.30	$609.20	$609.30