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 $162.81   6.691%   $173.7036   $173.70   $173.70   $173.70  
  Purchase #2 $182.57   9.382%   $199.6987   $199.70   $199.70   $199.70  
  Purchase #3 $135.47   10.781%   $150.075   $150.08   $150.10   $150.10  
  Purchase #4 $116.72   5.329%   $122.94   $122.94   $122.95   $122.90  
  Purchase #5 $100.56   10.383%   $111.0011   $111.00   $111.00   $111.00  
  Purchase #6 $242.70   10.128%   $267.2807   $267.28   $267.30   $267.30  
  Purchase #7 $184.31   8.524%   $200.0206   $200.02   $200.00   $200.00  
  7 purchase totals = $1,125.14       $1,224.7197   $1,224.72   $1,224.75   $1,224.70