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	$196.25	6.149%	$208.3174	$208.32	$208.30	$208.30
Purchase #2	$66.78	7.600%	$71.8553	$71.86	$71.85	$71.90
Purchase #3	$220.71	8.680%	$239.8676	$239.87	$239.85	$239.90
Purchase #4	$74.81	9.410%	$81.8496	$81.85	$81.85	$81.80
Purchase #5	$105.51	4.523%	$110.2822	$110.28	$110.30	$110.30
Purchase #6	$95.50	3.703%	$99.0364	$99.04	$99.05	$99.00
Purchase #7	$101.72	10.480%	$112.3803	$112.38	$112.40	$112.40
7 purchase totals =	$861.28		$923.5888	$923.60	$923.60	$923.60