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 $182.41   8.515%   $197.9422   $197.94   $197.95   $197.90  
  Purchase #2 $85.93   3.131%   $88.6205   $88.62   $88.60   $88.60  
  Purchase #3 $209.59   9.732%   $229.9873   $229.99   $230.00   $230.00  
  Purchase #4 $200.62   7.420%   $215.506   $215.51   $215.50   $215.50  
  Purchase #5 $35.27   10.840%   $39.0933   $39.09   $39.10   $39.10  
  Purchase #6 $77.89   8.417%   $84.446   $84.45   $84.45   $84.40  
  Purchase #7 $241.97   5.353%   $254.9227   $254.92   $254.90   $254.90  
  7 purchase totals = $1,033.68       $1,110.5180   $1,110.52   $1,110.50   $1,110.40