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	$213.80	12.377%	$240.262	$240.26	$240.25	$240.30
Purchase #2	$13.38	8.817%	$14.5597	$14.56	$14.55	$14.60
Purchase #3	$71.73	7.176%	$76.8773	$76.88	$76.90	$76.90
Purchase #4	$170.36	12.180%	$191.1098	$191.11	$191.10	$191.10
Purchase #5	$107.71	3.473%	$111.4508	$111.45	$111.45	$111.50
Purchase #6	$114.43	13.186%	$129.5187	$129.52	$129.50	$129.50
Purchase #7	$130.81	7.621%	$140.779	$140.78	$140.80	$140.80
7 purchase totals =	$822.22		$904.5573	$904.56	$904.55	$904.70