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	$193.40	13.839%	$220.1646	$220.16	$220.15	$220.20
Purchase #2	$77.58	5.501%	$81.8477	$81.85	$81.85	$81.80
Purchase #3	$237.93	12.473%	$267.607	$267.61	$267.60	$267.60
Purchase #4	$205.58	5.759%	$217.4194	$217.42	$217.40	$217.40
Purchase #5	$172.34	7.662%	$185.5447	$185.54	$185.55	$185.50
Purchase #6	$39.72	4.747%	$41.6055	$41.61	$41.60	$41.60
Purchase #7	$94.53	4.182%	$98.4832	$98.48	$98.50	$98.50
7 purchase totals =	$1,021.08		$1,112.6721	$1,112.67	$1,112.65	$1,112.60