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	$137.72	10.508%	$152.1916	$152.19	$152.20	$152.20
Purchase #2	$182.66	4.200%	$190.3317	$190.33	$190.35	$190.30
Purchase #3	$179.74	9.166%	$196.215	$196.22	$196.20	$196.20
Purchase #4	$153.94	6.755%	$164.3386	$164.34	$164.35	$164.30
Purchase #5	$194.67	5.322%	$205.0303	$205.03	$205.05	$205.00
Purchase #6	$86.38	12.841%	$97.4721	$97.47	$97.45	$97.50
Purchase #7	$56.86	7.733%	$61.257	$61.26	$61.25	$61.30
7 purchase totals =	$991.97		$1,066.8363	$1,066.84	$1,066.85	$1,066.80