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	$111.60	13.371%	$126.522	$126.52	$126.50	$126.50
Purchase #2	$127.38	4.494%	$133.1045	$133.10	$133.10	$133.10
Purchase #3	$42.45	3.172%	$43.7965	$43.80	$43.80	$43.80
Purchase #4	$42.78	4.789%	$44.8287	$44.83	$44.85	$44.80
Purchase #5	$125.82	7.849%	$135.6956	$135.70	$135.70	$135.70
Purchase #6	$35.53	6.134%	$37.7094	$37.71	$37.70	$37.70
Purchase #7	$148.77	7.854%	$160.4544	$160.45	$160.45	$160.50
7 purchase totals =	$634.33		$682.1111	$682.11	$682.10	$682.10