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	$155.60	5.432%	$164.0522	$164.05	$164.05	$164.10
Purchase #2	$208.68	9.435%	$228.369	$228.37	$228.35	$228.40
Purchase #3	$102.61	10.393%	$113.2743	$113.27	$113.25	$113.30
Purchase #4	$84.72	7.340%	$90.9384	$90.94	$90.95	$90.90
Purchase #5	$162.82	3.823%	$169.0446	$169.04	$169.05	$169.00
Purchase #6	$132.50	8.372%	$143.5929	$143.59	$143.60	$143.60
Purchase #7	$90.69	7.310%	$97.3194	$97.32	$97.30	$97.30
7 purchase totals =	$937.62		$1,006.5908	$1,006.58	$1,006.55	$1,006.60