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	$87.58	4.363%	$91.4011	$91.40	$91.40	$91.40
Purchase #2	$35.51	6.212%	$37.7159	$37.72	$37.70	$37.70
Purchase #3	$150.93	6.731%	$161.0891	$161.09	$161.10	$161.10
Purchase #4	$16.96	9.584%	$18.5854	$18.59	$18.60	$18.60
Purchase #5	$233.98	5.617%	$247.1227	$247.12	$247.10	$247.10
Purchase #6	$84.28	6.691%	$89.9192	$89.92	$89.90	$89.90
Purchase #7	$117.38	4.832%	$123.0518	$123.05	$123.05	$123.10
7 purchase totals =	$726.62		$768.8852	$768.89	$768.85	$768.90