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	$237.86	13.674%	$270.385	$270.39	$270.40	$270.40
Purchase #2	$46.61	13.551%	$52.9261	$52.93	$52.95	$52.90
Purchase #3	$29.25	6.681%	$31.2042	$31.20	$31.20	$31.20
Purchase #4	$57.77	3.366%	$59.7145	$59.71	$59.70	$59.70
Purchase #5	$33.97	5.700%	$35.9063	$35.91	$35.90	$35.90
Purchase #6	$132.87	8.732%	$144.4722	$144.47	$144.45	$144.50
Purchase #7	$89.75	13.264%	$101.6544	$101.65	$101.65	$101.70
7 purchase totals =	$628.08		$696.2627	$696.26	$696.25	$696.30