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 $43.86   6.394%   $46.6644   $46.66   $46.65   $46.70  
  Purchase #2 $99.26   5.213%   $104.4344   $104.43   $104.45   $104.40  
  Purchase #3 $85.76   12.142%   $96.173   $96.17   $96.15   $96.20  
  Purchase #4 $141.30   3.108%   $145.6916   $145.69   $145.70   $145.70  
  Purchase #5 $150.81   4.631%   $157.794   $157.79   $157.80   $157.80  
  Purchase #6 $143.28   4.725%   $150.05   $150.05   $150.05   $150.10  
  Purchase #7 $225.43   12.525%   $253.6651   $253.67   $253.65   $253.70  
  7 purchase totals = $889.70       $954.4725   $954.46   $954.45   $954.60