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	$193.76	13.653%	$220.2141	$220.21	$220.20	$220.20
Purchase #2	$60.53	8.509%	$65.6805	$65.68	$65.70	$65.70
Purchase #3	$139.83	8.127%	$151.194	$151.19	$151.20	$151.20
Purchase #4	$162.87	5.294%	$171.4923	$171.49	$171.50	$171.50
Purchase #5	$234.88	12.346%	$263.8783	$263.88	$263.90	$263.90
Purchase #6	$169.42	13.264%	$191.8919	$191.89	$191.90	$191.90
Purchase #7	$103.88	10.561%	$114.8508	$114.85	$114.85	$114.90
7 purchase totals =	$1,065.17		$1,179.2019	$1,179.19	$1,179.25	$1,179.30