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	$31.62	5.110%	$33.2358	$33.24	$33.25	$33.20
Purchase #2	$15.32	8.858%	$16.677	$16.68	$16.70	$16.70
Purchase #3	$168.69	10.193%	$185.8846	$185.88	$185.90	$185.90
Purchase #4	$127.36	3.231%	$131.475	$131.48	$131.50	$131.50
Purchase #5	$188.77	12.606%	$212.5663	$212.57	$212.55	$212.60
Purchase #6	$244.81	4.534%	$255.9097	$255.91	$255.90	$255.90
Purchase #7	$55.28	13.852%	$62.9374	$62.94	$62.95	$62.90
7 purchase totals =	$831.85		$898.6858	$898.70	$898.75	$898.70