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	$20.70	8.467%	$22.4527	$22.45	$22.45	$22.50
Purchase #2	$54.46	10.144%	$59.9844	$59.98	$60.00	$60.00
Purchase #3	$131.47	4.133%	$136.9037	$136.90	$136.90	$136.90
Purchase #4	$99.60	9.360%	$108.9226	$108.92	$108.90	$108.90
Purchase #5	$211.82	8.168%	$229.1215	$229.12	$229.10	$229.10
Purchase #6	$151.60	11.303%	$168.7353	$168.74	$168.75	$168.70
Purchase #7	$119.57	10.720%	$132.3879	$132.39	$132.40	$132.40
7 purchase totals =	$789.22		$858.5081	$858.50	$858.50	$858.50