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	$114.53	4.128%	$119.2578	$119.26	$119.25	$119.30
Purchase #2	$11.59	6.820%	$12.3804	$12.38	$12.40	$12.40
Purchase #3	$163.25	5.200%	$171.739	$171.74	$171.75	$171.70
Purchase #4	$35.50	12.289%	$39.8626	$39.86	$39.85	$39.90
Purchase #5	$69.79	12.509%	$78.52	$78.52	$78.50	$78.50
Purchase #6	$213.95	9.476%	$234.2239	$234.22	$234.20	$234.20
Purchase #7	$96.48	13.691%	$109.6891	$109.69	$109.70	$109.70
7 purchase totals =	$705.09		$765.6728	$765.67	$765.65	$765.70