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	$168.87	7.686%	$181.8493	$181.85	$181.85	$181.80
Purchase #2	$72.60	8.597%	$78.8414	$78.84	$78.85	$78.80
Purchase #3	$10.28	6.346%	$10.9324	$10.93	$10.95	$10.90
Purchase #4	$162.56	5.471%	$171.4537	$171.45	$171.45	$171.50
Purchase #5	$55.57	11.226%	$61.8083	$61.81	$61.80	$61.80
Purchase #6	$66.77	10.593%	$73.8429	$73.84	$73.85	$73.80
Purchase #7	$108.49	8.305%	$117.5001	$117.50	$117.50	$117.50
7 purchase totals =	$645.14		$696.2281	$696.22	$696.25	$696.10