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 $244.58   7.394%   $262.6642   $262.66   $262.65   $262.70  
  Purchase #2 $155.78   12.460%   $175.1902   $175.19   $175.20   $175.20  
  Purchase #3 $32.86   12.316%   $36.907   $36.91   $36.90   $36.90  
  Purchase #4 $59.29   13.776%   $67.4578   $67.46   $67.45   $67.50  
  Purchase #5 $203.78   12.235%   $228.7125   $228.71   $228.70   $228.70  
  Purchase #6 $175.99   5.799%   $186.1957   $186.20   $186.20   $186.20  
  Purchase #7 $158.50   10.750%   $175.5388   $175.54   $175.55   $175.50  
  7 purchase totals = $1,030.78       $1,132.6662   $1,132.67   $1,132.65   $1,132.70