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 $54.52   7.597%   $58.6619   $58.66   $58.65   $58.70  
  Purchase #2 $215.27   9.309%   $235.3095   $235.31   $235.30   $235.30  
  Purchase #3 $73.56   6.126%   $78.0663   $78.07   $78.05   $78.10  
  Purchase #4 $26.71   4.245%   $27.8438   $27.84   $27.85   $27.80  
  Purchase #5 $127.44   7.861%   $137.4581   $137.46   $137.45   $137.50  
  Purchase #6 $236.65   11.118%   $262.9607   $262.96   $262.95   $263.00  
  Purchase #7 $193.32   10.845%   $214.2856   $214.29   $214.30   $214.30  
  7 purchase totals = $927.47       $1,014.5859   $1,014.59   $1,014.55   $1,014.70