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	$125.33	9.648%	$137.4218	$137.42	$137.40	$137.40
Purchase #2	$6.80	9.298%	$7.4323	$7.43	$7.45	$7.40
Purchase #3	$48.57	9.683%	$53.273	$53.27	$53.25	$53.30
Purchase #4	$115.60	7.165%	$123.8827	$123.88	$123.90	$123.90
Purchase #5	$154.27	8.492%	$167.3706	$167.37	$167.35	$167.40
Purchase #6	$156.87	4.580%	$164.0546	$164.05	$164.05	$164.10
Purchase #7	$227.45	13.872%	$259.0019	$259.00	$259.00	$259.00
7 purchase totals =	$834.89		$912.4369	$912.42	$912.40	$912.50