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	$75.57	12.390%	$84.9331	$84.93	$84.95	$84.90
Purchase #2	$56.81	8.359%	$61.5587	$61.56	$61.55	$61.60
Purchase #3	$73.35	12.466%	$82.4938	$82.49	$82.50	$82.50
Purchase #4	$96.46	3.603%	$99.9355	$99.94	$99.95	$99.90
Purchase #5	$29.53	7.217%	$31.6612	$31.66	$31.65	$31.70
Purchase #6	$83.29	7.516%	$89.5501	$89.55	$89.55	$89.60
Purchase #7	$159.57	11.761%	$178.337	$178.34	$178.35	$178.30
7 purchase totals =	$574.58		$628.4694	$628.47	$628.50	$628.50