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	$118.82	4.267%	$123.89	$123.89	$123.90	$123.90
Purchase #2	$135.99	11.486%	$151.6098	$151.61	$151.60	$151.60
Purchase #3	$73.91	11.633%	$82.508	$82.51	$82.50	$82.50
Purchase #4	$234.89	13.194%	$265.8814	$265.88	$265.90	$265.90
Purchase #5	$35.80	8.116%	$38.7055	$38.71	$38.70	$38.70
Purchase #6	$179.28	3.674%	$185.8667	$185.87	$185.85	$185.90
Purchase #7	$180.93	8.151%	$195.6776	$195.68	$195.70	$195.70
7 purchase totals =	$959.62		$1,044.1390	$1,044.15	$1,044.15	$1,044.20