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	$244.89	3.586%	$253.6718	$253.67	$253.65	$253.70
Purchase #2	$118.26	6.480%	$125.9232	$125.92	$125.90	$125.90
Purchase #3	$216.36	3.342%	$223.5908	$223.59	$223.60	$223.60
Purchase #4	$150.79	3.402%	$155.9199	$155.92	$155.90	$155.90
Purchase #5	$37.57	4.252%	$39.1675	$39.17	$39.15	$39.20
Purchase #6	$128.86	12.395%	$144.8322	$144.83	$144.85	$144.80
Purchase #7	$143.83	8.842%	$156.5474	$156.55	$156.55	$156.50
7 purchase totals =	$1,040.56		$1,099.6528	$1,099.65	$1,099.60	$1,099.60