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	$40.57	10.472%	$44.8185	$44.82	$44.80	$44.80
Purchase #2	$100.69	6.308%	$107.0415	$107.04	$107.05	$107.00
Purchase #3	$177.31	6.688%	$189.1685	$189.17	$189.15	$189.20
Purchase #4	$221.63	12.127%	$248.5071	$248.51	$248.50	$248.50
Purchase #5	$199.63	7.559%	$214.72	$214.72	$214.70	$214.70
Purchase #6	$182.83	7.686%	$196.8823	$196.88	$196.90	$196.90
Purchase #7	$227.51	12.439%	$255.81	$255.81	$255.80	$255.80
7 purchase totals =	$1,150.17		$1,256.9479	$1,256.95	$1,256.90	$1,256.90