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	$129.72	11.272%	$144.342	$144.34	$144.35	$144.30
Purchase #2	$89.30	12.600%	$100.5518	$100.55	$100.55	$100.60
Purchase #3	$23.82	6.235%	$25.3052	$25.31	$25.30	$25.30
Purchase #4	$196.66	10.448%	$217.207	$217.21	$217.20	$217.20
Purchase #5	$119.86	3.499%	$124.0539	$124.05	$124.05	$124.10
Purchase #6	$124.40	12.605%	$140.0806	$140.08	$140.10	$140.10
Purchase #7	$109.52	9.461%	$119.8817	$119.88	$119.90	$119.90
7 purchase totals =	$793.28		$871.4222	$871.42	$871.45	$871.50