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	$213.50	12.813%	$240.8558	$240.86	$240.85	$240.90
Purchase #2	$36.59	7.519%	$39.3412	$39.34	$39.35	$39.30
Purchase #3	$83.51	6.845%	$89.2263	$89.23	$89.25	$89.20
Purchase #4	$126.41	11.386%	$140.803	$140.80	$140.80	$140.80
Purchase #5	$11.25	5.610%	$11.8811	$11.88	$11.90	$11.90
Purchase #6	$85.78	12.549%	$96.5445	$96.54	$96.55	$96.50
Purchase #7	$122.64	12.628%	$138.127	$138.13	$138.15	$138.10
7 purchase totals =	$679.68		$756.7789	$756.78	$756.85	$756.70