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	$112.53	5.600%	$118.8317	$118.83	$118.85	$118.80
Purchase #2	$183.90	6.607%	$196.0503	$196.05	$196.05	$196.10
Purchase #3	$115.95	13.285%	$131.354	$131.35	$131.35	$131.40
Purchase #4	$96.76	5.231%	$101.8215	$101.82	$101.80	$101.80
Purchase #5	$20.83	8.370%	$22.5735	$22.57	$22.55	$22.60
Purchase #6	$40.60	12.515%	$45.6811	$45.68	$45.70	$45.70
Purchase #7	$228.69	7.661%	$246.2099	$246.21	$246.20	$246.20
7 purchase totals =	$799.26		$862.5220	$862.51	$862.50	$862.60