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 $113.93   10.409%   $125.789   $125.79   $125.80   $125.80  
  Purchase #2 $126.26   12.121%   $141.564   $141.56   $141.55   $141.60  
  Purchase #3 $170.87   4.813%   $179.094   $179.09   $179.10   $179.10  
  Purchase #4 $212.96   11.249%   $236.9159   $236.92   $236.90   $236.90  
  Purchase #5 $107.61   8.587%   $116.8505   $116.85   $116.85   $116.90  
  Purchase #6 $25.43   11.611%   $28.3827   $28.38   $28.40   $28.40  
  Purchase #7 $32.31   5.156%   $33.9759   $33.98   $34.00   $34.00  
  7 purchase totals = $789.37       $862.5720   $862.57   $862.60   $862.70