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	$132.93	3.685%	$137.8285	$137.83	$137.85	$137.80
Purchase #2	$29.96	9.807%	$32.8982	$32.90	$32.90	$32.90
Purchase #3	$102.72	6.535%	$109.4328	$109.43	$109.45	$109.40
Purchase #4	$202.98	11.777%	$226.885	$226.89	$226.90	$226.90
Purchase #5	$211.46	4.655%	$221.3035	$221.30	$221.30	$221.30
Purchase #6	$164.28	3.442%	$169.9345	$169.93	$169.95	$169.90
Purchase #7	$172.29	5.346%	$181.5006	$181.50	$181.50	$181.50
7 purchase totals =	$1,016.62		$1,079.7831	$1,079.78	$1,079.85	$1,079.70