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	$166.47	4.661%	$174.2292	$174.23	$174.25	$174.20
Purchase #2	$248.54	5.282%	$261.6679	$261.67	$261.65	$261.70
Purchase #3	$146.39	6.336%	$155.6653	$155.67	$155.65	$155.70
Purchase #4	$180.32	8.822%	$196.2278	$196.23	$196.25	$196.20
Purchase #5	$243.76	4.159%	$253.898	$253.90	$253.90	$253.90
Purchase #6	$114.55	4.387%	$119.5753	$119.58	$119.60	$119.60
Purchase #7	$142.51	13.733%	$162.0809	$162.08	$162.10	$162.10
7 purchase totals =	$1,242.54		$1,323.3444	$1,323.36	$1,323.40	$1,323.40