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 $71.88   6.478%   $76.5364   $76.54   $76.55   $76.50  
  Purchase #2 $57.68   8.630%   $62.6578   $62.66   $62.65   $62.70  
  Purchase #3 $52.93   8.854%   $57.6164   $57.62   $57.60   $57.60  
  Purchase #4 $246.58   3.525%   $255.2719   $255.27   $255.25   $255.30  
  Purchase #5 $195.52   10.679%   $216.3996   $216.40   $216.40   $216.40  
  Purchase #6 $129.27   11.681%   $144.37   $144.37   $144.35   $144.40  
  Purchase #7 $214.35   7.495%   $230.4155   $230.42   $230.40   $230.40  
  7 purchase totals = $968.21       $1,043.2676   $1,043.28   $1,043.20   $1,043.30