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	$65.65	10.405%	$72.4809	$72.48	$72.50	$72.50
Purchase #2	$29.63	7.520%	$31.8582	$31.86	$31.85	$31.90
Purchase #3	$103.77	4.686%	$108.6327	$108.63	$108.65	$108.60
Purchase #4	$114.96	4.193%	$119.7803	$119.78	$119.80	$119.80
Purchase #5	$227.69	11.756%	$254.4572	$254.46	$254.45	$254.50
Purchase #6	$242.61	11.457%	$270.4058	$270.41	$270.40	$270.40
Purchase #7	$40.85	9.780%	$44.8451	$44.85	$44.85	$44.80
7 purchase totals =	$825.16		$902.4602	$902.47	$902.50	$902.50