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	$90.81	8.475%	$98.5061	$98.51	$98.50	$98.50
Purchase #2	$169.27	5.501%	$178.5815	$178.58	$178.60	$178.60
Purchase #3	$185.60	5.783%	$196.3332	$196.33	$196.35	$196.30
Purchase #4	$50.48	6.210%	$53.6148	$53.61	$53.60	$53.60
Purchase #5	$47.77	12.103%	$53.5516	$53.55	$53.55	$53.60
Purchase #6	$32.90	9.867%	$36.1462	$36.15	$36.15	$36.10
Purchase #7	$173.80	6.407%	$184.9354	$184.94	$184.95	$184.90
7 purchase totals =	$750.63		$801.6688	$801.67	$801.70	$801.60