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	$85.95	3.626%	$89.0665	$89.07	$89.05	$89.10
Purchase #2	$148.99	9.352%	$162.9235	$162.92	$162.90	$162.90
Purchase #3	$112.65	8.755%	$122.5125	$122.51	$122.50	$122.50
Purchase #4	$40.81	12.252%	$45.81	$45.81	$45.80	$45.80
Purchase #5	$144.87	4.619%	$151.5615	$151.56	$151.55	$151.60
Purchase #6	$199.64	8.184%	$215.9785	$215.98	$216.00	$216.00
Purchase #7	$222.85	9.210%	$243.3745	$243.37	$243.35	$243.40
7 purchase totals =	$955.76		$1,031.2270	$1,031.22	$1,031.15	$1,031.30