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	$94.57	3.235%	$97.6293	$97.63	$97.65	$97.60
Purchase #2	$24.48	5.564%	$25.8421	$25.84	$25.85	$25.80
Purchase #3	$27.43	7.835%	$29.5791	$29.58	$29.60	$29.60
Purchase #4	$37.35	10.150%	$41.141	$41.14	$41.15	$41.10
Purchase #5	$72.90	7.452%	$78.3325	$78.33	$78.35	$78.30
Purchase #6	$238.75	7.396%	$256.408	$256.41	$256.40	$256.40
Purchase #7	$48.54	10.207%	$53.4945	$53.49	$53.50	$53.50
7 purchase totals =	$544.02		$582.4265	$582.42	$582.50	$582.30