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 $58.63   5.660%   $61.9485   $61.95   $61.95   $61.90  
  Purchase #2 $149.83   7.598%   $161.2141   $161.21   $161.20   $161.20  
  Purchase #3 $216.39   6.192%   $229.7889   $229.79   $229.80   $229.80  
  Purchase #4 $178.72   6.350%   $190.0687   $190.07   $190.05   $190.10  
  Purchase #5 $24.58   11.568%   $27.4234   $27.42   $27.40   $27.40  
  Purchase #6 $159.79   10.853%   $177.132   $177.13   $177.15   $177.10  
  Purchase #7 $197.38   13.284%   $223.6   $223.60   $223.60   $223.60  
  7 purchase totals = $985.32       $1,071.1756   $1,071.17   $1,071.15   $1,071.10