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	$82.68	13.217%	$93.6078	$93.61	$93.60	$93.60
Purchase #2	$137.54	5.341%	$144.886	$144.89	$144.90	$144.90
Purchase #3	$164.95	9.699%	$180.9485	$180.95	$180.95	$180.90
Purchase #4	$51.57	3.846%	$53.5534	$53.55	$53.55	$53.60
Purchase #5	$118.47	7.534%	$127.3955	$127.40	$127.40	$127.40
Purchase #6	$185.81	7.702%	$200.1211	$200.12	$200.10	$200.10
Purchase #7	$54.54	7.298%	$58.5203	$58.52	$58.50	$58.50
7 purchase totals =	$795.56		$859.0326	$859.04	$859.00	$859.00