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	$164.76	8.625%	$178.9706	$178.97	$178.95	$179.00
Purchase #2	$128.95	8.136%	$139.4414	$139.44	$139.45	$139.40
Purchase #3	$114.67	4.270%	$119.5664	$119.57	$119.55	$119.60
Purchase #4	$28.89	13.682%	$32.8427	$32.84	$32.85	$32.80
Purchase #5	$219.39	9.411%	$240.0368	$240.04	$240.05	$240.00
Purchase #6	$62.53	4.758%	$65.5052	$65.51	$65.50	$65.50
Purchase #7	$114.33	7.838%	$123.2912	$123.29	$123.30	$123.30
7 purchase totals =	$833.52		$899.6543	$899.66	$899.65	$899.60