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	$154.37	6.697%	$164.7082	$164.71	$164.70	$164.70
Purchase #2	$32.53	8.510%	$35.2983	$35.30	$35.30	$35.30
Purchase #3	$130.79	10.266%	$144.2169	$144.22	$144.20	$144.20
Purchase #4	$105.78	4.811%	$110.8691	$110.87	$110.85	$110.90
Purchase #5	$81.45	10.726%	$90.1863	$90.19	$90.20	$90.20
Purchase #6	$119.71	13.783%	$136.2096	$136.21	$136.20	$136.20
Purchase #7	$98.47	7.149%	$105.5096	$105.51	$105.50	$105.50
7 purchase totals =	$723.10		$786.9980	$787.01	$786.95	$787.00