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	$99.39	12.239%	$111.5543	$111.55	$111.55	$111.60
Purchase #2	$69.95	3.367%	$72.3052	$72.31	$72.30	$72.30
Purchase #3	$75.53	5.367%	$79.5837	$79.58	$79.60	$79.60
Purchase #4	$49.51	10.652%	$54.7838	$54.78	$54.80	$54.80
Purchase #5	$177.41	5.343%	$186.889	$186.89	$186.90	$186.90
Purchase #6	$168.76	13.847%	$192.1282	$192.13	$192.15	$192.10
Purchase #7	$95.58	6.703%	$101.9867	$101.99	$102.00	$102.00
7 purchase totals =	$736.13		$799.2309	$799.23	$799.30	$799.30