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	$152.68	4.524%	$159.5872	$159.59	$159.60	$159.60
Purchase #2	$114.43	7.689%	$123.2285	$123.23	$123.25	$123.20
Purchase #3	$164.53	8.799%	$179.007	$179.01	$179.00	$179.00
Purchase #4	$181.93	3.678%	$188.6214	$188.62	$188.60	$188.60
Purchase #5	$90.30	13.556%	$102.5411	$102.54	$102.55	$102.50
Purchase #6	$75.71	7.297%	$81.2346	$81.23	$81.25	$81.20
Purchase #7	$34.47	10.592%	$38.1211	$38.12	$38.10	$38.10
7 purchase totals =	$814.05		$872.3409	$872.34	$872.35	$872.20