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	$248.58	4.257%	$259.1621	$259.16	$259.15	$259.20
Purchase #2	$232.67	10.413%	$256.8979	$256.90	$256.90	$256.90
Purchase #3	$163.52	9.714%	$179.4043	$179.40	$179.40	$179.40
Purchase #4	$30.57	4.774%	$32.0294	$32.03	$32.05	$32.00
Purchase #5	$199.82	6.535%	$212.8782	$212.88	$212.90	$212.90
Purchase #6	$187.77	6.800%	$200.5384	$200.54	$200.55	$200.50
Purchase #7	$212.73	3.167%	$219.4672	$219.47	$219.45	$219.50
7 purchase totals =	$1,275.66		$1,360.3775	$1,360.38	$1,360.40	$1,360.40