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	$68.95	13.657%	$78.3665	$78.37	$78.35	$78.40
Purchase #2	$198.34	5.220%	$208.6933	$208.69	$208.70	$208.70
Purchase #3	$35.80	4.622%	$37.4547	$37.45	$37.45	$37.50
Purchase #4	$109.78	9.632%	$120.354	$120.35	$120.35	$120.40
Purchase #5	$246.40	3.203%	$254.2922	$254.29	$254.30	$254.30
Purchase #6	$19.85	9.840%	$21.8032	$21.80	$21.80	$21.80
Purchase #7	$81.51	9.641%	$89.3684	$89.37	$89.35	$89.40
7 purchase totals =	$760.63		$810.3323	$810.32	$810.30	$810.50