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 $65.36   5.482%   $68.943   $68.94   $68.95   $68.90  
  Purchase #2 $242.39   10.437%   $267.6882   $267.69   $267.70   $267.70  
  Purchase #3 $56.39   8.469%   $61.1657   $61.17   $61.15   $61.20  
  Purchase #4 $170.52   13.844%   $194.1268   $194.13   $194.15   $194.10  
  Purchase #5 $243.40   5.811%   $257.544   $257.54   $257.55   $257.50  
  Purchase #6 $100.94   11.192%   $112.2372   $112.24   $112.25   $112.20  
  Purchase #7 $158.99   10.294%   $175.3564   $175.36   $175.35   $175.40  
  7 purchase totals = $1,037.99       $1,137.0613   $1,137.07   $1,137.10   $1,137.00