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	$53.39	4.582%	$55.8363	$55.84	$55.85	$55.80
Purchase #2	$106.90	9.874%	$117.4553	$117.46	$117.45	$117.50
Purchase #3	$71.38	4.766%	$74.782	$74.78	$74.80	$74.80
Purchase #4	$46.49	8.454%	$50.4203	$50.42	$50.40	$50.40
Purchase #5	$78.92	13.442%	$89.5284	$89.53	$89.55	$89.50
Purchase #6	$45.82	7.393%	$49.2075	$49.21	$49.20	$49.20
Purchase #7	$217.66	3.314%	$224.8733	$224.87	$224.85	$224.90
7 purchase totals =	$620.56		$662.1031	$662.11	$662.10	$662.10