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	$103.88	9.321%	$113.5627	$113.56	$113.55	$113.60
Purchase #2	$194.34	10.873%	$215.4706	$215.47	$215.45	$215.50
Purchase #3	$81.73	6.453%	$87.004	$87.00	$87.00	$87.00
Purchase #4	$157.63	8.851%	$171.5818	$171.58	$171.60	$171.60
Purchase #5	$85.59	6.856%	$91.4581	$91.46	$91.45	$91.50
Purchase #6	$108.82	13.386%	$123.3866	$123.39	$123.40	$123.40
Purchase #7	$59.43	4.208%	$61.9308	$61.93	$61.95	$61.90
7 purchase totals =	$791.42		$864.3946	$864.39	$864.40	$864.50