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	$65.76	10.580%	$72.7174	$72.72	$72.70	$72.70
Purchase #2	$89.49	6.356%	$95.178	$95.18	$95.20	$95.20
Purchase #3	$131.50	10.548%	$145.3706	$145.37	$145.35	$145.40
Purchase #4	$144.27	12.365%	$162.109	$162.11	$162.10	$162.10
Purchase #5	$209.68	3.664%	$217.3627	$217.36	$217.35	$217.40
Purchase #6	$157.50	13.300%	$178.4475	$178.45	$178.45	$178.40
Purchase #7	$32.94	6.381%	$35.0419	$35.04	$35.05	$35.00
7 purchase totals =	$831.14		$906.2271	$906.23	$906.20	$906.20