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	$65.61	6.550%	$69.9075	$69.91	$69.90	$69.90
Purchase #2	$33.39	11.783%	$37.3243	$37.32	$37.30	$37.30
Purchase #3	$132.57	11.635%	$147.9945	$147.99	$148.00	$148.00
Purchase #4	$122.67	13.431%	$139.1458	$139.15	$139.15	$139.10
Purchase #5	$223.56	3.704%	$231.8407	$231.84	$231.85	$231.80
Purchase #6	$32.46	5.727%	$34.319	$34.32	$34.30	$34.30
Purchase #7	$31.39	6.697%	$33.4922	$33.49	$33.50	$33.50
7 purchase totals =	$641.65		$694.0240	$694.02	$694.00	$693.90