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	$133.61	8.259%	$144.6448	$144.64	$144.65	$144.60
Purchase #2	$130.48	12.863%	$147.2636	$147.26	$147.25	$147.30
Purchase #3	$101.54	10.218%	$111.9154	$111.92	$111.90	$111.90
Purchase #4	$89.28	9.245%	$97.5339	$97.53	$97.55	$97.50
Purchase #5	$115.56	10.715%	$127.9423	$127.94	$127.95	$127.90
Purchase #6	$216.88	6.793%	$231.6127	$231.61	$231.60	$231.60
Purchase #7	$14.30	3.266%	$14.767	$14.77	$14.75	$14.80
7 purchase totals =	$801.65		$875.6797	$875.67	$875.65	$875.60