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	$126.91	3.227%	$131.0054	$131.01	$131.00	$131.00
Purchase #2	$159.38	7.424%	$171.2124	$171.21	$171.20	$171.20
Purchase #3	$202.27	9.790%	$222.0722	$222.07	$222.05	$222.10
Purchase #4	$140.61	10.605%	$155.5217	$155.52	$155.50	$155.50
Purchase #5	$177.85	12.224%	$199.5904	$199.59	$199.60	$199.60
Purchase #6	$168.96	9.193%	$184.4925	$184.49	$184.50	$184.50
Purchase #7	$27.90	4.268%	$29.0908	$29.09	$29.10	$29.10
7 purchase totals =	$1,003.88		$1,092.9854	$1,092.98	$1,092.95	$1,093.00