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	$52.31	13.434%	$59.3373	$59.34	$59.35	$59.30
Purchase #2	$202.96	3.501%	$210.0656	$210.07	$210.05	$210.10
Purchase #3	$74.86	8.236%	$81.0255	$81.03	$81.05	$81.00
Purchase #4	$76.78	13.403%	$87.0708	$87.07	$87.05	$87.10
Purchase #5	$248.46	4.534%	$259.7252	$259.73	$259.75	$259.70
Purchase #6	$78.59	5.512%	$82.9219	$82.92	$82.90	$82.90
Purchase #7	$88.75	7.320%	$95.2465	$95.25	$95.25	$95.20
7 purchase totals =	$822.71		$875.3928	$875.41	$875.40	$875.30