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	$112.82	10.670%	$124.8579	$124.86	$124.85	$124.90
Purchase #2	$114.89	5.139%	$120.7942	$120.79	$120.80	$120.80
Purchase #3	$142.78	7.723%	$153.8069	$153.81	$153.80	$153.80
Purchase #4	$88.94	10.873%	$98.6104	$98.61	$98.60	$98.60
Purchase #5	$207.46	12.778%	$233.9692	$233.97	$233.95	$234.00
Purchase #6	$170.58	8.561%	$185.1834	$185.18	$185.20	$185.20
Purchase #7	$79.57	7.662%	$85.6667	$85.67	$85.65	$85.70
7 purchase totals =	$917.04		$1,002.8887	$1,002.89	$1,002.85	$1,003.00