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	$222.67	8.379%	$241.3275	$241.33	$241.35	$241.30
Purchase #2	$66.32	8.492%	$71.9519	$71.95	$71.95	$72.00
Purchase #3	$146.46	4.442%	$152.9658	$152.97	$152.95	$153.00
Purchase #4	$20.34	3.314%	$21.0141	$21.01	$21.00	$21.00
Purchase #5	$33.66	10.232%	$37.1041	$37.10	$37.10	$37.10
Purchase #6	$155.95	7.803%	$168.1188	$168.12	$168.10	$168.10
Purchase #7	$116.27	6.859%	$124.245	$124.25	$124.25	$124.20
7 purchase totals =	$761.67		$816.7272	$816.73	$816.70	$816.70