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	$134.49	10.706%	$148.8885	$148.89	$148.90	$148.90
Purchase #2	$150.69	12.343%	$169.2897	$169.29	$169.30	$169.30
Purchase #3	$37.78	7.339%	$40.5527	$40.55	$40.55	$40.60
Purchase #4	$187.31	8.463%	$203.162	$203.16	$203.15	$203.20
Purchase #5	$79.30	5.143%	$83.3784	$83.38	$83.40	$83.40
Purchase #6	$116.35	8.496%	$126.2351	$126.24	$126.25	$126.20
Purchase #7	$249.51	8.802%	$271.4719	$271.47	$271.45	$271.50
7 purchase totals =	$955.43		$1,042.9783	$1,042.98	$1,043.00	$1,043.10