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	$131.90	7.593%	$141.9152	$141.92	$141.90	$141.90
Purchase #2	$156.89	5.680%	$165.8014	$165.80	$165.80	$165.80
Purchase #3	$83.91	10.709%	$92.8959	$92.90	$92.90	$92.90
Purchase #4	$77.45	7.513%	$83.2688	$83.27	$83.25	$83.30
Purchase #5	$107.89	11.862%	$120.6879	$120.69	$120.70	$120.70
Purchase #6	$162.45	8.322%	$175.9691	$175.97	$175.95	$176.00
Purchase #7	$44.46	13.661%	$50.5337	$50.53	$50.55	$50.50
7 purchase totals =	$764.95		$831.0720	$831.08	$831.05	$831.10