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	$145.86	3.242%	$150.5888	$150.59	$150.60	$150.60
Purchase #2	$10.98	3.539%	$11.3686	$11.37	$11.35	$11.40
Purchase #3	$51.62	7.730%	$55.6102	$55.61	$55.60	$55.60
Purchase #4	$242.61	7.154%	$259.9663	$259.97	$259.95	$260.00
Purchase #5	$61.73	8.292%	$66.8487	$66.85	$66.85	$66.80
Purchase #6	$94.68	11.563%	$105.6278	$105.63	$105.65	$105.60
Purchase #7	$41.88	9.296%	$45.7732	$45.77	$45.75	$45.80
7 purchase totals =	$649.36		$695.7836	$695.79	$695.75	$695.80