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	$163.93	7.803%	$176.7215	$176.72	$176.70	$176.70
Purchase #2	$168.67	13.108%	$190.7793	$190.78	$190.80	$190.80
Purchase #3	$105.38	4.251%	$109.8597	$109.86	$109.85	$109.90
Purchase #4	$172.44	5.386%	$181.7276	$181.73	$181.75	$181.70
Purchase #5	$187.72	7.517%	$201.8309	$201.83	$201.85	$201.80
Purchase #6	$87.77	13.863%	$99.9376	$99.94	$99.95	$99.90
Purchase #7	$78.72	5.502%	$83.0512	$83.05	$83.05	$83.10
7 purchase totals =	$964.63		$1,043.9078	$1,043.91	$1,043.95	$1,043.90