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	$116.30	10.710%	$128.7557	$128.76	$128.75	$128.80
Purchase #2	$91.90	9.166%	$100.3236	$100.32	$100.30	$100.30
Purchase #3	$110.68	5.231%	$116.4697	$116.47	$116.45	$116.50
Purchase #4	$83.27	4.433%	$86.9614	$86.96	$86.95	$87.00
Purchase #5	$161.99	10.661%	$179.2598	$179.26	$179.25	$179.30
Purchase #6	$250.93	6.734%	$267.8276	$267.83	$267.85	$267.80
Purchase #7	$33.51	4.710%	$35.0883	$35.09	$35.10	$35.10
7 purchase totals =	$848.58		$914.6861	$914.69	$914.65	$914.80