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	$133.45	6.372%	$141.9534	$141.95	$141.95	$142.00
Purchase #2	$114.91	8.826%	$125.052	$125.05	$125.05	$125.10
Purchase #3	$135.56	6.104%	$143.8346	$143.83	$143.85	$143.80
Purchase #4	$192.62	8.792%	$209.5552	$209.56	$209.55	$209.60
Purchase #5	$146.61	11.134%	$162.9336	$162.93	$162.95	$162.90
Purchase #6	$168.83	10.530%	$186.6078	$186.61	$186.60	$186.60
Purchase #7	$113.27	10.248%	$124.8779	$124.88	$124.90	$124.90
7 purchase totals =	$1,005.25		$1,094.8145	$1,094.81	$1,094.85	$1,094.90