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 $151.71   7.199%   $162.6316   $162.63   $162.65   $162.60  
  Purchase #2 $179.68   4.272%   $187.3559   $187.36   $187.35   $187.40  
  Purchase #3 $82.26   5.301%   $86.6206   $86.62   $86.60   $86.60  
  Purchase #4 $129.38   5.340%   $136.2889   $136.29   $136.30   $136.30  
  Purchase #5 $212.44   8.653%   $230.8224   $230.82   $230.80   $230.80  
  Purchase #6 $40.46   13.863%   $46.069   $46.07   $46.05   $46.10  
  Purchase #7 $151.45   5.762%   $160.1765   $160.18   $160.20   $160.20  
  7 purchase totals = $947.38       $1,009.9649   $1,009.97   $1,009.95   $1,010.00