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	$6.68	8.173%	$7.226	$7.23	$7.25	$7.20
Purchase #2	$66.88	8.154%	$72.3334	$72.33	$72.35	$72.30
Purchase #3	$68.70	5.655%	$72.585	$72.59	$72.60	$72.60
Purchase #4	$82.39	8.529%	$89.417	$89.42	$89.40	$89.40
Purchase #5	$176.88	7.319%	$189.8258	$189.83	$189.85	$189.80
Purchase #6	$5.85	12.638%	$6.5893	$6.59	$6.60	$6.60
Purchase #7	$205.55	4.225%	$214.2345	$214.23	$214.25	$214.20
7 purchase totals =	$612.93		$652.2110	$652.22	$652.30	$652.10