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	$84.56	9.452%	$92.5526	$92.55	$92.55	$92.60
Purchase #2	$87.61	10.260%	$96.5988	$96.60	$96.60	$96.60
Purchase #3	$160.57	7.334%	$172.3462	$172.35	$172.35	$172.30
Purchase #4	$105.76	5.792%	$111.8856	$111.89	$111.90	$111.90
Purchase #5	$117.55	7.315%	$126.1488	$126.15	$126.15	$126.10
Purchase #6	$27.94	7.276%	$29.9729	$29.97	$29.95	$30.00
Purchase #7	$223.94	8.665%	$243.3444	$243.34	$243.35	$243.30
7 purchase totals =	$807.93		$872.8493	$872.85	$872.85	$872.80