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	$117.39	13.703%	$133.476	$133.48	$133.50	$133.50
Purchase #2	$211.30	6.443%	$224.9141	$224.91	$224.90	$224.90
Purchase #3	$130.66	10.126%	$143.8906	$143.89	$143.90	$143.90
Purchase #4	$37.86	4.836%	$39.6909	$39.69	$39.70	$39.70
Purchase #5	$112.88	3.528%	$116.8624	$116.86	$116.85	$116.90
Purchase #6	$223.80	8.647%	$243.152	$243.15	$243.15	$243.20
Purchase #7	$231.85	5.243%	$244.0059	$244.01	$244.00	$244.00
7 purchase totals =	$1,065.74		$1,145.9919	$1,145.99	$1,146.00	$1,146.10