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 $119.42   6.297%   $126.9399   $126.94   $126.95   $126.90  
  Purchase #2 $95.90   10.140%   $105.6243   $105.62   $105.60   $105.60  
  Purchase #3 $218.41   12.787%   $246.3381   $246.34   $246.35   $246.30  
  Purchase #4 $23.40   13.220%   $26.4935   $26.49   $26.50   $26.50  
  Purchase #5 $238.51   5.739%   $252.1981   $252.20   $252.20   $252.20  
  Purchase #6 $54.30   3.380%   $56.1353   $56.14   $56.15   $56.10  
  Purchase #7 $192.43   10.128%   $211.9193   $211.92   $211.90   $211.90  
  7 purchase totals = $942.37       $1,025.6485   $1,025.65   $1,025.65   $1,025.50