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	$105.32	6.303%	$111.9583	$111.96	$111.95	$112.00
Purchase #2	$175.66	10.724%	$194.4978	$194.50	$194.50	$194.50
Purchase #3	$156.88	7.866%	$169.2202	$169.22	$169.20	$169.20
Purchase #4	$142.56	7.645%	$153.4587	$153.46	$153.45	$153.50
Purchase #5	$126.62	7.523%	$136.1456	$136.15	$136.15	$136.10
Purchase #6	$113.34	12.411%	$127.4066	$127.41	$127.40	$127.40
Purchase #7	$19.40	5.510%	$20.4689	$20.47	$20.45	$20.50
7 purchase totals =	$839.78		$913.1561	$913.17	$913.10	$913.20