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	$59.38	13.463%	$67.3743	$67.37	$67.35	$67.40
Purchase #2	$92.49	7.385%	$99.3204	$99.32	$99.30	$99.30
Purchase #3	$218.83	8.237%	$236.855	$236.86	$236.85	$236.90
Purchase #4	$33.79	9.487%	$36.9957	$37.00	$37.00	$37.00
Purchase #5	$79.85	13.444%	$90.585	$90.59	$90.60	$90.60
Purchase #6	$75.71	10.508%	$83.6656	$83.67	$83.65	$83.70
Purchase #7	$117.72	12.560%	$132.5056	$132.51	$132.50	$132.50
7 purchase totals =	$677.77		$747.3016	$747.32	$747.25	$747.40