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	$78.25	13.245%	$88.6142	$88.61	$88.60	$88.60
Purchase #2	$176.58	10.207%	$194.6035	$194.60	$194.60	$194.60
Purchase #3	$56.89	5.411%	$59.9683	$59.97	$59.95	$60.00
Purchase #4	$15.89	3.425%	$16.4342	$16.43	$16.45	$16.40
Purchase #5	$118.63	13.494%	$134.6379	$134.64	$134.65	$134.60
Purchase #6	$109.96	12.310%	$123.4961	$123.50	$123.50	$123.50
Purchase #7	$201.45	5.300%	$212.1269	$212.13	$212.15	$212.10
7 purchase totals =	$757.65		$829.8811	$829.88	$829.90	$829.80