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	$70.49	3.234%	$72.7696	$72.77	$72.75	$72.80
Purchase #2	$156.70	5.185%	$164.8249	$164.82	$164.80	$164.80
Purchase #3	$98.71	9.127%	$107.7193	$107.72	$107.70	$107.70
Purchase #4	$105.29	8.776%	$114.5303	$114.53	$114.55	$114.50
Purchase #5	$126.95	3.508%	$131.4034	$131.40	$131.40	$131.40
Purchase #6	$96.50	8.823%	$105.0142	$105.01	$105.00	$105.00
Purchase #7	$187.48	12.721%	$211.3293	$211.33	$211.35	$211.30
7 purchase totals =	$842.12		$907.5910	$907.58	$907.55	$907.50