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	$25.83	11.122%	$28.7028	$28.70	$28.70	$28.70
Purchase #2	$49.68	5.607%	$52.4656	$52.47	$52.45	$52.50
Purchase #3	$54.43	9.311%	$59.498	$59.50	$59.50	$59.50
Purchase #4	$131.41	8.228%	$142.2224	$142.22	$142.20	$142.20
Purchase #5	$21.47	8.560%	$23.3078	$23.31	$23.30	$23.30
Purchase #6	$164.85	11.150%	$183.2308	$183.23	$183.25	$183.20
Purchase #7	$216.32	11.644%	$241.5083	$241.51	$241.50	$241.50
7 purchase totals =	$663.99		$730.9357	$730.94	$730.90	$730.90