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	$98.58	5.515%	$104.0167	$104.02	$104.00	$104.00
Purchase #2	$39.93	5.711%	$42.2104	$42.21	$42.20	$42.20
Purchase #3	$33.92	9.140%	$37.0203	$37.02	$37.00	$37.00
Purchase #4	$89.72	3.569%	$92.9221	$92.92	$92.90	$92.90
Purchase #5	$161.86	4.622%	$169.3412	$169.34	$169.35	$169.30
Purchase #6	$120.36	9.226%	$131.4644	$131.46	$131.45	$131.50
Purchase #7	$208.52	10.466%	$230.3437	$230.34	$230.35	$230.30
7 purchase totals =	$752.89		$807.3188	$807.31	$807.25	$807.20