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 $113.93   5.205%   $119.8601   $119.86   $119.85   $119.90  
  Purchase #2 $32.80   7.479%   $35.2531   $35.25   $35.25   $35.30  
  Purchase #3 $50.64   6.667%   $54.0162   $54.02   $54.00   $54.00  
  Purchase #4 $20.58   3.800%   $21.362   $21.36   $21.35   $21.40  
  Purchase #5 $226.38   3.688%   $234.7289   $234.73   $234.75   $234.70  
  Purchase #6 $244.98   5.157%   $257.6136   $257.61   $257.60   $257.60  
  Purchase #7 $203.27   7.703%   $218.9279   $218.93   $218.95   $218.90  
  7 purchase totals = $892.58       $941.7618   $941.76   $941.75   $941.80