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	$40.72	8.691%	$44.259	$44.26	$44.25	$44.30
Purchase #2	$245.79	11.667%	$274.4663	$274.47	$274.45	$274.50
Purchase #3	$37.32	8.595%	$40.5277	$40.53	$40.55	$40.50
Purchase #4	$17.25	13.179%	$19.5234	$19.52	$19.50	$19.50
Purchase #5	$220.65	8.164%	$238.6639	$238.66	$238.65	$238.70
Purchase #6	$234.68	3.755%	$243.4922	$243.49	$243.50	$243.50
Purchase #7	$88.31	4.141%	$91.9669	$91.97	$91.95	$92.00
7 purchase totals =	$884.72		$952.8994	$952.90	$952.85	$953.00