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 $195.33   8.347%   $211.6342   $211.63   $211.65   $211.60  
  Purchase #2 $62.57   13.168%   $70.8092   $70.81   $70.80   $70.80  
  Purchase #3 $28.36   9.185%   $30.9649   $30.96   $30.95   $31.00  
  Purchase #4 $201.87   5.703%   $213.3826   $213.38   $213.40   $213.40  
  Purchase #5 $134.65   6.350%   $143.2003   $143.20   $143.20   $143.20  
  Purchase #6 $222.40   10.421%   $245.5763   $245.58   $245.60   $245.60  
  Purchase #7 $113.44   3.217%   $117.0894   $117.09   $117.10   $117.10  
  7 purchase totals = $958.62       $1,032.6569   $1,032.65   $1,032.70   $1,032.70