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	$140.36	12.440%	$157.8208	$157.82	$157.80	$157.80
Purchase #2	$18.41	3.718%	$19.0945	$19.09	$19.10	$19.10
Purchase #3	$176.25	7.369%	$189.2379	$189.24	$189.25	$189.20
Purchase #4	$116.84	13.163%	$132.2196	$132.22	$132.20	$132.20
Purchase #5	$85.76	4.298%	$89.446	$89.45	$89.45	$89.40
Purchase #6	$87.45	3.573%	$90.5746	$90.57	$90.55	$90.60
Purchase #7	$77.32	6.233%	$82.1394	$82.14	$82.15	$82.10
7 purchase totals =	$702.39		$760.5328	$760.53	$760.50	$760.40