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	$180.58	6.124%	$191.6387	$191.64	$191.65	$191.60
Purchase #2	$234.32	9.372%	$256.2805	$256.28	$256.30	$256.30
Purchase #3	$82.55	9.610%	$90.4831	$90.48	$90.50	$90.50
Purchase #4	$78.72	7.473%	$84.6027	$84.60	$84.60	$84.60
Purchase #5	$199.86	7.505%	$214.8595	$214.86	$214.85	$214.90
Purchase #6	$157.81	7.467%	$169.5937	$169.59	$169.60	$169.60
Purchase #7	$90.78	7.424%	$97.5195	$97.52	$97.50	$97.50
7 purchase totals =	$1,024.62		$1,104.9777	$1,104.97	$1,105.00	$1,105.00