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	$181.43	8.499%	$196.8497	$196.85	$196.85	$196.80
Purchase #2	$192.71	4.125%	$200.6593	$200.66	$200.65	$200.70
Purchase #3	$206.39	12.697%	$232.5953	$232.60	$232.60	$232.60
Purchase #4	$75.53	4.336%	$78.805	$78.81	$78.80	$78.80
Purchase #5	$40.53	12.724%	$45.687	$45.69	$45.70	$45.70
Purchase #6	$206.51	3.259%	$213.2402	$213.24	$213.25	$213.20
Purchase #7	$11.54	7.170%	$12.3674	$12.37	$12.35	$12.40
7 purchase totals =	$914.64		$980.2039	$980.22	$980.20	$980.20