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 $157.36   10.577%   $174.004   $174.00   $174.00   $174.00  
  Purchase #2 $97.50   7.568%   $104.8788   $104.88   $104.90   $104.90  
  Purchase #3 $111.54   10.165%   $122.878   $122.88   $122.90   $122.90  
  Purchase #4 $64.34   4.502%   $67.2366   $67.24   $67.25   $67.20  
  Purchase #5 $235.61   11.756%   $263.3083   $263.31   $263.30   $263.30  
  Purchase #6 $215.95   9.382%   $236.2104   $236.21   $236.20   $236.20  
  Purchase #7 $72.59   10.475%   $80.1938   $80.19   $80.20   $80.20  
  7 purchase totals = $954.89       $1,048.7099   $1,048.71   $1,048.75   $1,048.70