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	$31.31	3.801%	$32.5001	$32.50	$32.50	$32.50
Purchase #2	$57.25	7.459%	$61.5203	$61.52	$61.50	$61.50
Purchase #3	$238.78	12.849%	$269.4608	$269.46	$269.45	$269.50
Purchase #4	$213.69	12.849%	$241.147	$241.15	$241.15	$241.10
Purchase #5	$156.76	9.221%	$171.2148	$171.21	$171.20	$171.20
Purchase #6	$34.71	12.208%	$38.9474	$38.95	$38.95	$38.90
Purchase #7	$241.67	5.450%	$254.841	$254.84	$254.85	$254.80
7 purchase totals =	$974.17		$1,069.6314	$1,069.63	$1,069.60	$1,069.50