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	$88.28	4.691%	$92.4212	$92.42	$92.40	$92.40
Purchase #2	$189.34	10.596%	$209.4025	$209.40	$209.40	$209.40
Purchase #3	$170.40	11.626%	$190.2107	$190.21	$190.20	$190.20
Purchase #4	$40.91	7.686%	$44.0543	$44.05	$44.05	$44.10
Purchase #5	$51.92	5.853%	$54.9589	$54.96	$54.95	$55.00
Purchase #6	$152.56	11.682%	$170.3821	$170.38	$170.40	$170.40
Purchase #7	$213.43	4.237%	$222.473	$222.47	$222.45	$222.50
7 purchase totals =	$906.84		$983.9027	$983.89	$983.85	$984.00