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	$146.52	4.372%	$152.9259	$152.93	$152.95	$152.90
Purchase #2	$124.32	9.629%	$136.2908	$136.29	$136.30	$136.30
Purchase #3	$172.43	11.696%	$192.5974	$192.60	$192.60	$192.60
Purchase #4	$44.45	6.861%	$47.4997	$47.50	$47.50	$47.50
Purchase #5	$106.95	10.437%	$118.1124	$118.11	$118.10	$118.10
Purchase #6	$50.67	10.377%	$55.928	$55.93	$55.95	$55.90
Purchase #7	$44.54	12.333%	$50.0331	$50.03	$50.05	$50.00
7 purchase totals =	$689.88		$753.3873	$753.39	$753.45	$753.30