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	$156.78	11.326%	$174.5369	$174.54	$174.55	$174.50
Purchase #2	$181.93	7.853%	$196.217	$196.22	$196.20	$196.20
Purchase #3	$155.61	9.478%	$170.3587	$170.36	$170.35	$170.40
Purchase #4	$136.90	13.445%	$155.3062	$155.31	$155.30	$155.30
Purchase #5	$205.65	10.645%	$227.5414	$227.54	$227.55	$227.50
Purchase #6	$169.45	13.311%	$192.0055	$192.01	$192.00	$192.00
Purchase #7	$95.55	10.451%	$105.5359	$105.54	$105.55	$105.50
7 purchase totals =	$1,101.87		$1,221.5016	$1,221.52	$1,221.50	$1,221.40