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	$82.66	4.517%	$86.3938	$86.39	$86.40	$86.40
Purchase #2	$225.58	13.872%	$256.8725	$256.87	$256.85	$256.90
Purchase #3	$131.89	11.638%	$147.2394	$147.24	$147.25	$147.20
Purchase #4	$60.75	11.568%	$67.7776	$67.78	$67.80	$67.80
Purchase #5	$101.54	3.692%	$105.2889	$105.29	$105.30	$105.30
Purchase #6	$12.59	7.137%	$13.4885	$13.49	$13.50	$13.50
Purchase #7	$138.30	12.704%	$155.8696	$155.87	$155.85	$155.90
7 purchase totals =	$753.31		$832.9303	$832.93	$832.95	$833.00