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	$58.63	4.843%	$61.4695	$61.47	$61.45	$61.50
Purchase #2	$124.63	5.709%	$131.7451	$131.75	$131.75	$131.70
Purchase #3	$31.49	11.708%	$35.1768	$35.18	$35.20	$35.20
Purchase #4	$83.38	8.188%	$90.2072	$90.21	$90.20	$90.20
Purchase #5	$239.49	11.130%	$266.1452	$266.15	$266.15	$266.10
Purchase #6	$83.25	9.151%	$90.8682	$90.87	$90.85	$90.90
Purchase #7	$22.51	5.756%	$23.8057	$23.81	$23.80	$23.80
7 purchase totals =	$643.38		$699.4177	$699.44	$699.40	$699.40