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	$65.98	9.690%	$72.3735	$72.37	$72.35	$72.40
Purchase #2	$207.57	11.670%	$231.7934	$231.79	$231.80	$231.80
Purchase #3	$173.49	12.531%	$195.23	$195.23	$195.25	$195.20
Purchase #4	$134.46	5.733%	$142.1686	$142.17	$142.15	$142.20
Purchase #5	$92.93	9.650%	$101.8977	$101.90	$101.90	$101.90
Purchase #6	$172.40	10.713%	$190.8692	$190.87	$190.85	$190.90
Purchase #7	$6.83	7.131%	$7.317	$7.32	$7.30	$7.30
7 purchase totals =	$853.66		$941.6494	$941.65	$941.60	$941.70