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	$187.93	12.526%	$211.4701	$211.47	$211.45	$211.50
Purchase #2	$26.74	3.356%	$27.6374	$27.64	$27.65	$27.60
Purchase #3	$205.48	6.338%	$218.5033	$218.50	$218.50	$218.50
Purchase #4	$188.40	8.469%	$204.3556	$204.36	$204.35	$204.40
Purchase #5	$152.36	8.853%	$165.8484	$165.85	$165.85	$165.80
Purchase #6	$129.43	11.609%	$144.4555	$144.46	$144.45	$144.50
Purchase #7	$158.90	6.182%	$168.7232	$168.72	$168.70	$168.70
7 purchase totals =	$1,049.24		$1,140.9935	$1,141.00	$1,140.95	$1,141.00