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	$63.80	5.406%	$67.249	$67.25	$67.25	$67.20
Purchase #2	$94.65	6.520%	$100.8212	$100.82	$100.80	$100.80
Purchase #3	$91.26	6.440%	$97.1371	$97.14	$97.15	$97.10
Purchase #4	$22.78	5.455%	$24.0226	$24.02	$24.00	$24.00
Purchase #5	$96.93	5.786%	$102.5384	$102.54	$102.55	$102.50
Purchase #6	$38.32	13.347%	$43.4346	$43.43	$43.45	$43.40
Purchase #7	$161.43	12.498%	$181.6055	$181.61	$181.60	$181.60
7 purchase totals =	$569.17		$616.8084	$616.81	$616.80	$616.60