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 $81.92   6.117%   $86.931   $86.93   $86.95   $86.90  
  Purchase #2 $186.26   7.695%   $200.5927   $200.59   $200.60   $200.60  
  Purchase #3 $226.98   8.529%   $246.3391   $246.34   $246.35   $246.30  
  Purchase #4 $91.85   6.601%   $97.913   $97.91   $97.90   $97.90  
  Purchase #5 $245.33   5.542%   $258.9262   $258.93   $258.95   $258.90  
  Purchase #6 $229.70   8.865%   $250.0629   $250.06   $250.05   $250.10  
  Purchase #7 $123.41   3.600%   $127.8528   $127.85   $127.85   $127.90  
  7 purchase totals = $1,185.45       $1,268.6177   $1,268.61   $1,268.65   $1,268.60