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	$62.73	6.391%	$66.7391	$66.74	$66.75	$66.70
Purchase #2	$209.38	5.626%	$221.1597	$221.16	$221.15	$221.20
Purchase #3	$53.95	10.487%	$59.6077	$59.61	$59.60	$59.60
Purchase #4	$72.27	8.292%	$78.2626	$78.26	$78.25	$78.30
Purchase #5	$6.62	9.160%	$7.2264	$7.23	$7.25	$7.20
Purchase #6	$152.53	6.348%	$162.2126	$162.21	$162.20	$162.20
Purchase #7	$49.93	7.269%	$53.5594	$53.56	$53.55	$53.60
7 purchase totals =	$607.41		$648.7675	$648.77	$648.75	$648.80