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	$128.38	4.277%	$133.8708	$133.87	$133.85	$133.90
Purchase #2	$107.45	8.194%	$116.2545	$116.25	$116.25	$116.30
Purchase #3	$132.65	7.421%	$142.494	$142.49	$142.50	$142.50
Purchase #4	$71.31	3.601%	$73.8779	$73.88	$73.90	$73.90
Purchase #5	$39.46	8.602%	$42.8543	$42.85	$42.85	$42.90
Purchase #6	$64.56	10.452%	$71.3078	$71.31	$71.30	$71.30
Purchase #7	$132.63	10.310%	$146.3042	$146.30	$146.30	$146.30
7 purchase totals =	$676.44		$726.9635	$726.95	$726.95	$727.10