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	$239.37	10.513%	$264.535	$264.54	$264.55	$264.50
Purchase #2	$91.48	11.407%	$101.9151	$101.92	$101.90	$101.90
Purchase #3	$40.53	6.217%	$43.0498	$43.05	$43.05	$43.00
Purchase #4	$153.92	5.624%	$162.5765	$162.58	$162.60	$162.60
Purchase #5	$80.36	8.143%	$86.9037	$86.90	$86.90	$86.90
Purchase #6	$142.45	7.507%	$153.1437	$153.14	$153.15	$153.10
Purchase #7	$227.50	10.579%	$251.5672	$251.57	$251.55	$251.60
7 purchase totals =	$975.61		$1,063.6910	$1,063.70	$1,063.70	$1,063.60