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 $53.93   8.558%   $58.5453   $58.55   $58.55   $58.50  
  Purchase #2 $224.87   13.344%   $254.8767   $254.88   $254.90   $254.90  
  Purchase #3 $91.72   7.202%   $98.3257   $98.33   $98.35   $98.30  
  Purchase #4 $28.66   8.754%   $31.1689   $31.17   $31.15   $31.20  
  Purchase #5 $96.34   5.507%   $101.6454   $101.65   $101.65   $101.60  
  Purchase #6 $244.27   8.408%   $264.8082   $264.81   $264.80   $264.80  
  Purchase #7 $196.83   9.826%   $216.1705   $216.17   $216.15   $216.20  
  7 purchase totals = $936.62       $1,025.5407   $1,025.56   $1,025.55   $1,025.50