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 $192.52   4.786%   $201.734   $201.73   $201.75   $201.70  
  Purchase #2 $164.36   4.138%   $171.1612   $171.16   $171.15   $171.20  
  Purchase #3 $174.38   13.233%   $197.4557   $197.46   $197.45   $197.50  
  Purchase #4 $68.33   5.603%   $72.1585   $72.16   $72.15   $72.20  
  Purchase #5 $135.60   11.621%   $151.3581   $151.36   $151.35   $151.40  
  Purchase #6 $216.29   4.546%   $226.1225   $226.12   $226.10   $226.10  
  Purchase #7 $9.61   6.763%   $10.2599   $10.26   $10.25   $10.30  
  7 purchase totals = $961.09       $1,030.2499   $1,030.25   $1,030.20   $1,030.40