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	$164.63	9.733%	$180.6534	$180.65	$180.65	$180.70
Purchase #2	$6.30	8.816%	$6.8554	$6.86	$6.85	$6.90
Purchase #3	$245.43	8.196%	$265.5454	$265.55	$265.55	$265.50
Purchase #4	$153.64	9.625%	$168.4279	$168.43	$168.45	$168.40
Purchase #5	$86.50	3.321%	$89.3727	$89.37	$89.35	$89.40
Purchase #6	$198.31	5.719%	$209.6513	$209.65	$209.65	$209.70
Purchase #7	$92.96	5.535%	$98.1053	$98.11	$98.10	$98.10
7 purchase totals =	$947.77		$1,018.6114	$1,018.62	$1,018.60	$1,018.70