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	$152.68	5.738%	$161.4408	$161.44	$161.45	$161.40
Purchase #2	$73.51	11.309%	$81.8232	$81.82	$81.80	$81.80
Purchase #3	$193.64	11.281%	$215.4845	$215.48	$215.50	$215.50
Purchase #4	$167.37	7.240%	$179.4876	$179.49	$179.50	$179.50
Purchase #5	$212.53	4.541%	$222.181	$222.18	$222.20	$222.20
Purchase #6	$246.78	13.659%	$280.4877	$280.49	$280.50	$280.50
Purchase #7	$83.72	5.750%	$88.5339	$88.53	$88.55	$88.50
7 purchase totals =	$1,130.23		$1,229.4387	$1,229.43	$1,229.50	$1,229.40