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	$136.88	11.430%	$152.5254	$152.53	$152.55	$152.50
Purchase #2	$27.42	7.603%	$29.5047	$29.50	$29.50	$29.50
Purchase #3	$122.88	4.713%	$128.6713	$128.67	$128.65	$128.70
Purchase #4	$13.54	4.314%	$14.1241	$14.12	$14.10	$14.10
Purchase #5	$13.35	13.510%	$15.1536	$15.15	$15.15	$15.20
Purchase #6	$164.71	12.624%	$185.503	$185.50	$185.50	$185.50
Purchase #7	$100.39	11.463%	$111.8977	$111.90	$111.90	$111.90
7 purchase totals =	$579.17		$637.3798	$637.37	$637.35	$637.40