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	$176.58	13.764%	$200.8845	$200.88	$200.90	$200.90
Purchase #2	$169.64	5.864%	$179.5877	$179.59	$179.60	$179.60
Purchase #3	$28.59	9.296%	$31.2477	$31.25	$31.25	$31.20
Purchase #4	$172.42	9.206%	$188.293	$188.29	$188.30	$188.30
Purchase #5	$60.35	11.743%	$67.4369	$67.44	$67.45	$67.40
Purchase #6	$164.32	3.677%	$170.362	$170.36	$170.35	$170.40
Purchase #7	$191.82	5.536%	$202.4392	$202.44	$202.45	$202.40
7 purchase totals =	$963.72		$1,040.2510	$1,040.25	$1,040.30	$1,040.20