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	$68.63	6.245%	$72.9159	$72.92	$72.90	$72.90
Purchase #2	$230.28	4.870%	$241.4946	$241.49	$241.50	$241.50
Purchase #3	$127.25	7.440%	$136.7174	$136.72	$136.70	$136.70
Purchase #4	$137.54	9.718%	$150.9061	$150.91	$150.90	$150.90
Purchase #5	$206.32	3.644%	$213.8383	$213.84	$213.85	$213.80
Purchase #6	$32.43	3.175%	$33.4597	$33.46	$33.45	$33.50
Purchase #7	$98.99	9.795%	$108.6861	$108.69	$108.70	$108.70
7 purchase totals =	$901.44		$958.0181	$958.03	$958.00	$958.00