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	$86.98	11.212%	$96.7322	$96.73	$96.75	$96.70
Purchase #2	$208.30	10.356%	$229.8715	$229.87	$229.85	$229.90
Purchase #3	$195.71	11.340%	$217.9035	$217.90	$217.90	$217.90
Purchase #4	$159.56	7.862%	$172.1046	$172.10	$172.10	$172.10
Purchase #5	$207.56	11.602%	$231.6411	$231.64	$231.65	$231.60
Purchase #6	$71.92	8.128%	$77.7657	$77.77	$77.75	$77.80
Purchase #7	$41.60	10.283%	$45.8777	$45.88	$45.90	$45.90
7 purchase totals =	$971.63		$1,071.8963	$1,071.89	$1,071.90	$1,071.90