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	$206.59	9.824%	$226.8854	$226.89	$226.90	$226.90
Purchase #2	$98.44	13.676%	$111.9027	$111.90	$111.90	$111.90
Purchase #3	$23.71	11.808%	$26.5097	$26.51	$26.50	$26.50
Purchase #4	$76.73	11.713%	$85.7174	$85.72	$85.70	$85.70
Purchase #5	$213.37	13.842%	$242.9047	$242.90	$242.90	$242.90
Purchase #6	$44.35	6.848%	$47.3871	$47.39	$47.40	$47.40
Purchase #7	$214.70	13.517%	$243.721	$243.72	$243.70	$243.70
7 purchase totals =	$877.89		$985.0280	$985.03	$985.00	$985.00