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 $186.37   4.604%   $194.9505   $194.95   $194.95   $195.00  
  Purchase #2 $57.87   13.507%   $65.6865   $65.69   $65.70   $65.70  
  Purchase #3 $204.44   13.846%   $232.7468   $232.75   $232.75   $232.70  
  Purchase #4 $168.38   10.777%   $186.5263   $186.53   $186.55   $186.50  
  Purchase #5 $197.50   11.252%   $219.7227   $219.72   $219.70   $219.70  
  Purchase #6 $58.36   5.519%   $61.5809   $61.58   $61.60   $61.60  
  Purchase #7 $227.62   3.171%   $234.8378   $234.84   $234.85   $234.80  
  7 purchase totals = $1,100.54       $1,196.0515   $1,196.06   $1,196.10   $1,196.00