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	$97.89	7.674%	$105.4021	$105.40	$105.40	$105.40
Purchase #2	$192.59	11.249%	$214.2544	$214.25	$214.25	$214.30
Purchase #3	$172.38	9.131%	$188.12	$188.12	$188.10	$188.10
Purchase #4	$242.74	5.139%	$255.2144	$255.21	$255.20	$255.20
Purchase #5	$68.71	4.410%	$71.7401	$71.74	$71.75	$71.70
Purchase #6	$90.98	10.464%	$100.5001	$100.50	$100.50	$100.50
Purchase #7	$49.90	9.224%	$54.5028	$54.50	$54.50	$54.50
7 purchase totals =	$915.19		$989.7339	$989.72	$989.70	$989.70