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	$154.97	6.863%	$165.6056	$165.61	$165.60	$165.60
Purchase #2	$98.59	11.111%	$109.5443	$109.54	$109.55	$109.50
Purchase #3	$63.81	13.583%	$72.4773	$72.48	$72.50	$72.50
Purchase #4	$180.62	6.490%	$192.3422	$192.34	$192.35	$192.30
Purchase #5	$105.34	12.655%	$118.6708	$118.67	$118.65	$118.70
Purchase #6	$201.55	6.115%	$213.8748	$213.87	$213.85	$213.90
Purchase #7	$38.92	9.593%	$42.6536	$42.65	$42.65	$42.70
7 purchase totals =	$843.80		$915.1686	$915.16	$915.15	$915.20