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 $161.81   7.527%   $173.9894   $173.99   $174.00   $174.00  
  Purchase #2 $64.66   12.441%   $72.7044   $72.70   $72.70   $72.70  
  Purchase #3 $155.80   8.194%   $168.5663   $168.57   $168.55   $168.60  
  Purchase #4 $245.86   10.511%   $271.7023   $271.70   $271.70   $271.70  
  Purchase #5 $9.94   7.273%   $10.6629   $10.66   $10.65   $10.70  
  Purchase #6 $208.89   6.625%   $222.729   $222.73   $222.75   $222.70  
  Purchase #7 $96.99   6.415%   $103.2119   $103.21   $103.20   $103.20  
  7 purchase totals = $943.95       $1,023.5662   $1,023.56   $1,023.55   $1,023.60