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	$53.28	12.780%	$60.0892	$60.09	$60.10	$60.10
Purchase #2	$209.50	13.298%	$237.3593	$237.36	$237.35	$237.40
Purchase #3	$232.27	13.491%	$263.6055	$263.61	$263.60	$263.60
Purchase #4	$66.60	8.372%	$72.1758	$72.18	$72.20	$72.20
Purchase #5	$139.50	13.578%	$158.4413	$158.44	$158.45	$158.40
Purchase #6	$23.51	4.625%	$24.5973	$24.60	$24.60	$24.60
Purchase #7	$124.50	12.118%	$139.5869	$139.59	$139.60	$139.60
7 purchase totals =	$849.16		$955.8553	$955.87	$955.90	$955.90