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 $71.29   3.139%   $73.5278   $73.53   $73.55   $73.50  
  Purchase #2 $245.70   3.652%   $254.673   $254.67   $254.65   $254.70  
  Purchase #3 $164.60   9.781%   $180.6995   $180.70   $180.70   $180.70  
  Purchase #4 $207.93   6.389%   $221.2146   $221.21   $221.20   $221.20  
  Purchase #5 $235.85   11.261%   $262.4091   $262.41   $262.40   $262.40  
  Purchase #6 $166.26   8.180%   $179.8601   $179.86   $179.85   $179.90  
  Purchase #7 $59.41   6.257%   $63.1273   $63.13   $63.15   $63.10  
  7 purchase totals = $1,151.04       $1,235.5114   $1,235.51   $1,235.50   $1,235.50