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	$162.67	5.807%	$172.1162	$172.12	$172.10	$172.10
Purchase #2	$20.37	4.417%	$21.2697	$21.27	$21.25	$21.30
Purchase #3	$194.90	10.281%	$214.9377	$214.94	$214.95	$214.90
Purchase #4	$234.93	9.652%	$257.6054	$257.61	$257.60	$257.60
Purchase #5	$94.85	8.167%	$102.5964	$102.60	$102.60	$102.60
Purchase #6	$56.55	10.678%	$62.5884	$62.59	$62.60	$62.60
Purchase #7	$234.84	9.161%	$256.3537	$256.35	$256.35	$256.40
7 purchase totals =	$999.11		$1,087.4675	$1,087.48	$1,087.45	$1,087.50