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	$161.89	3.212%	$167.0899	$167.09	$167.10	$167.10
Purchase #2	$40.81	4.667%	$42.7146	$42.71	$42.70	$42.70
Purchase #3	$20.25	3.455%	$20.9496	$20.95	$20.95	$20.90
Purchase #4	$43.80	10.713%	$48.4923	$48.49	$48.50	$48.50
Purchase #5	$166.29	13.132%	$188.1272	$188.13	$188.15	$188.10
Purchase #6	$84.30	9.160%	$92.0219	$92.02	$92.00	$92.00
Purchase #7	$177.35	13.268%	$200.8808	$200.88	$200.90	$200.90
7 purchase totals =	$694.69		$760.2763	$760.27	$760.30	$760.20