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	$113.31	11.691%	$126.5571	$126.56	$126.55	$126.60
Purchase #2	$222.51	5.341%	$234.3943	$234.39	$234.40	$234.40
Purchase #3	$37.76	7.437%	$40.5682	$40.57	$40.55	$40.60
Purchase #4	$159.37	4.811%	$167.0373	$167.04	$167.05	$167.00
Purchase #5	$63.93	13.282%	$72.4212	$72.42	$72.40	$72.40
Purchase #6	$168.65	13.752%	$191.8427	$191.84	$191.85	$191.80
Purchase #7	$149.70	3.216%	$154.5144	$154.51	$154.50	$154.50
7 purchase totals =	$915.23		$987.3352	$987.33	$987.30	$987.30