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	$187.50	11.725%	$209.4844	$209.48	$209.50	$209.50
Purchase #2	$76.57	6.431%	$81.4942	$81.49	$81.50	$81.50
Purchase #3	$188.71	12.827%	$212.9158	$212.92	$212.90	$212.90
Purchase #4	$87.82	6.220%	$93.2824	$93.28	$93.30	$93.30
Purchase #5	$30.32	8.275%	$32.829	$32.83	$32.85	$32.80
Purchase #6	$23.51	4.258%	$24.5111	$24.51	$24.50	$24.50
Purchase #7	$34.86	12.757%	$39.3071	$39.31	$39.30	$39.30
7 purchase totals =	$629.29		$693.8240	$693.82	$693.85	$693.80