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	$118.74	12.152%	$133.1693	$133.17	$133.15	$133.20
Purchase #2	$73.38	7.477%	$78.8666	$78.87	$78.85	$78.90
Purchase #3	$197.64	11.268%	$219.9101	$219.91	$219.90	$219.90
Purchase #4	$180.94	3.859%	$187.9225	$187.92	$187.90	$187.90
Purchase #5	$112.86	12.724%	$127.2203	$127.22	$127.20	$127.20
Purchase #6	$101.28	12.725%	$114.1679	$114.17	$114.15	$114.20
Purchase #7	$92.74	7.595%	$99.7836	$99.78	$99.80	$99.80
7 purchase totals =	$877.58		$961.0403	$961.04	$960.95	$961.10