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	$165.57	9.691%	$181.6154	$181.62	$181.60	$181.60
Purchase #2	$240.35	10.724%	$266.1251	$266.13	$266.15	$266.10
Purchase #3	$105.57	3.500%	$109.265	$109.27	$109.25	$109.30
Purchase #4	$195.45	11.248%	$217.4342	$217.43	$217.45	$217.40
Purchase #5	$246.54	11.263%	$274.3078	$274.31	$274.30	$274.30
Purchase #6	$160.50	11.680%	$179.2464	$179.25	$179.25	$179.20
Purchase #7	$237.66	11.848%	$265.818	$265.82	$265.80	$265.80
7 purchase totals =	$1,351.64		$1,493.8119	$1,493.83	$1,493.80	$1,493.70