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	$132.31	13.630%	$150.3439	$150.34	$150.35	$150.30
Purchase #2	$225.82	13.443%	$256.177	$256.18	$256.20	$256.20
Purchase #3	$158.58	13.714%	$180.3277	$180.33	$180.35	$180.30
Purchase #4	$103.77	12.482%	$116.7226	$116.72	$116.70	$116.70
Purchase #5	$121.98	7.849%	$131.5542	$131.55	$131.55	$131.60
Purchase #6	$43.55	3.327%	$44.9989	$45.00	$45.00	$45.00
Purchase #7	$165.72	8.156%	$179.2361	$179.24	$179.25	$179.20
7 purchase totals =	$951.73		$1,059.3604	$1,059.36	$1,059.40	$1,059.30