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	$108.66	9.830%	$119.3413	$119.34	$119.35	$119.30
Purchase #2	$179.95	10.643%	$199.1021	$199.10	$199.10	$199.10
Purchase #3	$214.89	13.719%	$244.3708	$244.37	$244.35	$244.40
Purchase #4	$87.63	6.740%	$93.5363	$93.54	$93.55	$93.50
Purchase #5	$148.26	11.242%	$164.9274	$164.93	$164.95	$164.90
Purchase #6	$141.80	4.704%	$148.4703	$148.47	$148.45	$148.50
Purchase #7	$232.90	9.694%	$255.4773	$255.48	$255.50	$255.50
7 purchase totals =	$1,114.09		$1,225.2255	$1,225.23	$1,225.25	$1,225.20