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	$88.48	8.340%	$95.8592	$95.86	$95.85	$95.90
Purchase #2	$227.32	7.723%	$244.8759	$244.88	$244.90	$244.90
Purchase #3	$36.93	10.631%	$40.856	$40.86	$40.85	$40.90
Purchase #4	$202.34	13.529%	$229.7146	$229.71	$229.70	$229.70
Purchase #5	$105.83	9.511%	$115.8955	$115.90	$115.90	$115.90
Purchase #6	$49.36	5.176%	$51.9149	$51.91	$51.90	$51.90
Purchase #7	$28.26	11.452%	$31.4963	$31.50	$31.50	$31.50
7 purchase totals =	$738.52		$810.6124	$810.62	$810.60	$810.70