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	$109.32	7.497%	$117.5157	$117.52	$117.50	$117.50
Purchase #2	$198.47	7.446%	$213.2481	$213.25	$213.25	$213.20
Purchase #3	$23.35	6.680%	$24.9098	$24.91	$24.90	$24.90
Purchase #4	$200.96	6.679%	$214.3821	$214.38	$214.40	$214.40
Purchase #5	$207.48	7.485%	$223.0099	$223.01	$223.00	$223.00
Purchase #6	$112.75	4.697%	$118.0459	$118.05	$118.05	$118.00
Purchase #7	$63.84	5.767%	$67.5217	$67.52	$67.50	$67.50
7 purchase totals =	$916.17		$978.6332	$978.64	$978.60	$978.50