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	$84.73	7.291%	$90.9077	$90.91	$90.90	$90.90
Purchase #2	$86.94	3.388%	$89.8855	$89.89	$89.90	$89.90
Purchase #3	$31.59	7.266%	$33.8853	$33.89	$33.90	$33.90
Purchase #4	$119.46	6.255%	$126.9322	$126.93	$126.95	$126.90
Purchase #5	$222.80	11.371%	$248.1346	$248.13	$248.15	$248.10
Purchase #6	$177.79	13.493%	$201.7792	$201.78	$201.80	$201.80
Purchase #7	$158.85	13.141%	$179.7245	$179.72	$179.70	$179.70
7 purchase totals =	$882.16		$971.2490	$971.25	$971.30	$971.20