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	$245.95	6.601%	$262.1852	$262.19	$262.20	$262.20
Purchase #2	$134.89	7.798%	$145.4087	$145.41	$145.40	$145.40
Purchase #3	$96.60	6.697%	$103.0693	$103.07	$103.05	$103.10
Purchase #4	$38.89	8.434%	$42.17	$42.17	$42.15	$42.20
Purchase #5	$156.99	9.189%	$171.4158	$171.42	$171.40	$171.40
Purchase #6	$210.36	11.659%	$234.8859	$234.89	$234.90	$234.90
Purchase #7	$239.35	10.259%	$263.9049	$263.90	$263.90	$263.90
7 purchase totals =	$1,123.03		$1,223.0398	$1,223.05	$1,223.00	$1,223.10