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 $174.27   10.564%   $192.6799   $192.68   $192.70   $192.70  
  Purchase #2 $245.79   9.105%   $268.1692   $268.17   $268.15   $268.20  
  Purchase #3 $161.84   11.581%   $180.5827   $180.58   $180.60   $180.60  
  Purchase #4 $212.44   8.769%   $231.0689   $231.07   $231.05   $231.10  
  Purchase #5 $155.62   7.340%   $167.0425   $167.04   $167.05   $167.00  
  Purchase #6 $223.96   8.299%   $242.5464   $242.55   $242.55   $242.50  
  Purchase #7 $172.37   8.257%   $186.6026   $186.60   $186.60   $186.60  
  7 purchase totals = $1,346.29       $1,468.6922   $1,468.69   $1,468.70   $1,468.70