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	$58.54	11.320%	$65.1667	$65.17	$65.15	$65.20
Purchase #2	$126.89	3.802%	$131.7144	$131.71	$131.70	$131.70
Purchase #3	$56.95	9.634%	$62.4366	$62.44	$62.45	$62.40
Purchase #4	$125.88	9.184%	$137.4408	$137.44	$137.45	$137.40
Purchase #5	$243.34	6.511%	$259.1839	$259.18	$259.20	$259.20
Purchase #6	$95.31	13.445%	$108.1244	$108.12	$108.10	$108.10
Purchase #7	$19.66	6.503%	$20.9385	$20.94	$20.95	$20.90
7 purchase totals =	$726.57		$785.0053	$785.00	$785.00	$784.90