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	$24.29	5.380%	$25.5968	$25.60	$25.60	$25.60
Purchase #2	$159.47	10.105%	$175.5844	$175.58	$175.60	$175.60
Purchase #3	$171.47	5.562%	$181.0072	$181.01	$181.00	$181.00
Purchase #4	$169.43	12.443%	$190.5122	$190.51	$190.50	$190.50
Purchase #5	$249.63	3.544%	$258.4769	$258.48	$258.50	$258.50
Purchase #6	$80.63	7.572%	$86.7353	$86.74	$86.75	$86.70
Purchase #7	$221.61	9.476%	$242.6098	$242.61	$242.60	$242.60
7 purchase totals =	$1,076.53		$1,160.5226	$1,160.53	$1,160.55	$1,160.50