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	$136.34	3.522%	$141.1419	$141.14	$141.15	$141.10
Purchase #2	$77.79	5.625%	$82.1657	$82.17	$82.15	$82.20
Purchase #3	$213.78	12.214%	$239.8911	$239.89	$239.90	$239.90
Purchase #4	$134.93	3.389%	$139.5028	$139.50	$139.50	$139.50
Purchase #5	$121.70	3.618%	$126.1031	$126.10	$126.10	$126.10
Purchase #6	$98.94	11.665%	$110.4814	$110.48	$110.50	$110.50
Purchase #7	$75.83	8.147%	$82.0079	$82.01	$82.00	$82.00
7 purchase totals =	$859.31		$921.2939	$921.29	$921.30	$921.30