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 $90.34   5.166%   $95.007   $95.01   $95.00   $95.00  
  Purchase #2 $117.99   6.709%   $125.9059   $125.91   $125.90   $125.90  
  Purchase #3 $8.47   7.153%   $9.0759   $9.08   $9.10   $9.10  
  Purchase #4 $17.81   4.553%   $18.6209   $18.62   $18.60   $18.60  
  Purchase #5 $136.61   10.660%   $151.1726   $151.17   $151.15   $151.20  
  Purchase #6 $217.53   12.529%   $244.7843   $244.78   $244.80   $244.80  
  Purchase #7 $207.79   12.115%   $232.9638   $232.96   $232.95   $233.00  
  7 purchase totals = $796.54       $877.5304   $877.53   $877.50   $877.60