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 $71.84   5.415%   $75.7301   $75.73   $75.75   $75.70  
  Purchase #2 $84.46   10.227%   $93.0977   $93.10   $93.10   $93.10  
  Purchase #3 $44.57   10.369%   $49.1915   $49.19   $49.20   $49.20  
  Purchase #4 $235.98   3.112%   $243.3237   $243.32   $243.30   $243.30  
  Purchase #5 $124.34   13.147%   $140.687   $140.69   $140.70   $140.70  
  Purchase #6 $28.42   13.673%   $32.3059   $32.31   $32.30   $32.30  
  Purchase #7 $113.45   5.699%   $119.9155   $119.92   $119.90   $119.90  
  7 purchase totals = $703.06       $754.2514   $754.26   $754.25   $754.20