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	$147.56	7.835%	$159.1213	$159.12	$159.10	$159.10
Purchase #2	$132.48	3.776%	$137.4824	$137.48	$137.50	$137.50
Purchase #3	$106.38	8.681%	$115.6148	$115.61	$115.60	$115.60
Purchase #4	$239.98	6.446%	$255.4491	$255.45	$255.45	$255.40
Purchase #5	$196.34	4.527%	$205.2283	$205.23	$205.25	$205.20
Purchase #6	$10.82	5.610%	$11.427	$11.43	$11.45	$11.40
Purchase #7	$68.68	13.827%	$78.1764	$78.18	$78.20	$78.20
7 purchase totals =	$902.24		$962.4993	$962.50	$962.55	$962.40