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	$223.37	10.739%	$247.3577	$247.36	$247.35	$247.40
Purchase #2	$176.67	5.225%	$185.901	$185.90	$185.90	$185.90
Purchase #3	$61.27	12.316%	$68.816	$68.82	$68.80	$68.80
Purchase #4	$154.78	12.300%	$173.8179	$173.82	$173.80	$173.80
Purchase #5	$92.85	7.413%	$99.733	$99.73	$99.75	$99.70
Purchase #6	$56.57	5.496%	$59.6791	$59.68	$59.70	$59.70
Purchase #7	$193.61	9.321%	$211.6564	$211.66	$211.65	$211.70
7 purchase totals =	$959.12		$1,046.9611	$1,046.97	$1,046.95	$1,047.00