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 $216.98   5.638%   $229.2133   $229.21   $229.20   $229.20  
  Purchase #2 $34.70   10.544%   $38.3588   $38.36   $38.35   $38.40  
  Purchase #3 $57.97   3.301%   $59.8836   $59.88   $59.90   $59.90  
  Purchase #4 $92.55   5.211%   $97.3728   $97.37   $97.35   $97.40  
  Purchase #5 $192.28   6.329%   $204.4494   $204.45   $204.45   $204.40  
  Purchase #6 $146.91   10.706%   $162.6382   $162.64   $162.65   $162.60  
  Purchase #7 $201.92   10.130%   $222.3745   $222.37   $222.35   $222.40  
  7 purchase totals = $943.31       $1,014.2906   $1,014.28   $1,014.25   $1,014.30