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 $85.46   9.541%   $93.6137   $93.61   $93.60   $93.60  
  Purchase #2 $143.99   4.699%   $150.7561   $150.76   $150.75   $150.80  
  Purchase #3 $176.58   8.507%   $191.6017   $191.60   $191.60   $191.60  
  Purchase #4 $35.65   10.439%   $39.3715   $39.37   $39.35   $39.40  
  Purchase #5 $8.87   8.505%   $9.6244   $9.62   $9.60   $9.60  
  Purchase #6 $146.44   7.135%   $156.8885   $156.89   $156.90   $156.90  
  Purchase #7 $237.88   6.817%   $254.0963   $254.10   $254.10   $254.10  
  7 purchase totals = $834.87       $895.9522   $895.95   $895.90   $896.00