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	$87.35	4.519%	$91.2973	$91.30	$91.30	$91.30
Purchase #2	$162.40	7.109%	$173.945	$173.95	$173.95	$173.90
Purchase #3	$32.39	9.210%	$35.3731	$35.37	$35.35	$35.40
Purchase #4	$212.48	6.302%	$225.8705	$225.87	$225.85	$225.90
Purchase #5	$54.58	8.694%	$59.3252	$59.33	$59.35	$59.30
Purchase #6	$41.79	4.741%	$43.7713	$43.77	$43.75	$43.80
Purchase #7	$75.39	8.197%	$81.5697	$81.57	$81.55	$81.60
7 purchase totals =	$666.38		$711.1521	$711.16	$711.10	$711.20