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	$59.74	13.561%	$67.8413	$67.84	$67.85	$67.80
Purchase #2	$161.58	3.476%	$167.1965	$167.20	$167.20	$167.20
Purchase #3	$81.33	9.660%	$89.1865	$89.19	$89.20	$89.20
Purchase #4	$168.85	6.737%	$180.2254	$180.23	$180.25	$180.20
Purchase #5	$96.96	9.733%	$106.3971	$106.40	$106.40	$106.40
Purchase #6	$85.82	3.650%	$88.9524	$88.95	$88.95	$89.00
Purchase #7	$249.43	6.475%	$265.5806	$265.58	$265.60	$265.60
7 purchase totals =	$903.71		$965.3798	$965.39	$965.45	$965.40