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	$110.33	8.225%	$119.4046	$119.40	$119.40	$119.40
Purchase #2	$100.45	11.367%	$111.8682	$111.87	$111.85	$111.90
Purchase #3	$190.50	8.601%	$206.8849	$206.88	$206.90	$206.90
Purchase #4	$37.31	9.410%	$40.8209	$40.82	$40.80	$40.80
Purchase #5	$141.40	8.323%	$153.1687	$153.17	$153.15	$153.20
Purchase #6	$12.46	7.241%	$13.3622	$13.36	$13.35	$13.40
Purchase #7	$207.66	6.398%	$220.9461	$220.95	$220.95	$220.90
7 purchase totals =	$800.11		$866.4556	$866.45	$866.40	$866.50