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	$190.85	3.193%	$196.9438	$196.94	$196.95	$196.90
Purchase #2	$46.79	11.735%	$52.2808	$52.28	$52.30	$52.30
Purchase #3	$141.50	12.328%	$158.9441	$158.94	$158.95	$158.90
Purchase #4	$63.41	5.163%	$66.6839	$66.68	$66.70	$66.70
Purchase #5	$112.83	13.859%	$128.4671	$128.47	$128.45	$128.50
Purchase #6	$63.30	5.835%	$66.9936	$66.99	$67.00	$67.00
Purchase #7	$64.28	10.443%	$70.9928	$70.99	$71.00	$71.00
7 purchase totals =	$682.96		$741.3061	$741.29	$741.35	$741.30