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 $126.29   12.141%   $141.6229   $141.62   $141.60   $141.60  
  Purchase #2 $87.69   5.408%   $92.4323   $92.43   $92.45   $92.40  
  Purchase #3 $9.34   7.724%   $10.0614   $10.06   $10.05   $10.10  
  Purchase #4 $31.52   4.436%   $32.9182   $32.92   $32.90   $32.90  
  Purchase #5 $127.93   4.192%   $133.2928   $133.29   $133.30   $133.30  
  Purchase #6 $180.73   4.699%   $189.2225   $189.22   $189.20   $189.20  
  Purchase #7 $103.79   12.217%   $116.47   $116.47   $116.45   $116.50  
  7 purchase totals = $667.29       $716.0201   $716.01   $715.95   $716.00