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	$147.72	13.814%	$168.126	$168.13	$168.15	$168.10
Purchase #2	$65.85	11.748%	$73.5861	$73.59	$73.60	$73.60
Purchase #3	$80.37	9.413%	$87.9352	$87.94	$87.95	$87.90
Purchase #4	$123.42	7.227%	$132.3396	$132.34	$132.35	$132.30
Purchase #5	$72.91	7.460%	$78.3491	$78.35	$78.35	$78.30
Purchase #6	$140.66	12.249%	$157.8894	$157.89	$157.90	$157.90
Purchase #7	$30.96	3.634%	$32.0851	$32.09	$32.10	$32.10
7 purchase totals =	$661.89		$730.3105	$730.33	$730.40	$730.20