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	$212.69	11.327%	$236.7814	$236.78	$236.80	$236.80
Purchase #2	$104.89	11.303%	$116.7457	$116.75	$116.75	$116.70
Purchase #3	$83.93	8.860%	$91.3662	$91.37	$91.35	$91.40
Purchase #4	$33.69	10.302%	$37.1607	$37.16	$37.15	$37.20
Purchase #5	$32.56	4.685%	$34.0854	$34.09	$34.10	$34.10
Purchase #6	$79.82	7.454%	$85.7698	$85.77	$85.75	$85.80
Purchase #7	$151.74	4.840%	$159.0842	$159.08	$159.10	$159.10
7 purchase totals =	$699.32		$760.9934	$761.00	$761.00	$761.10