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	$145.75	9.115%	$159.0351	$159.04	$159.05	$159.00
Purchase #2	$119.37	9.713%	$130.9644	$130.96	$130.95	$131.00
Purchase #3	$57.25	4.480%	$59.8148	$59.81	$59.80	$59.80
Purchase #4	$103.42	13.431%	$117.3103	$117.31	$117.30	$117.30
Purchase #5	$143.44	13.761%	$163.1788	$163.18	$163.20	$163.20
Purchase #6	$76.90	7.406%	$82.5952	$82.60	$82.60	$82.60
Purchase #7	$19.53	5.605%	$20.6247	$20.62	$20.60	$20.60
7 purchase totals =	$665.66		$733.5233	$733.52	$733.50	$733.50