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 $214.59   12.425%   $241.2528   $241.25   $241.25   $241.30  
  Purchase #2 $102.97   9.446%   $112.6965   $112.70   $112.70   $112.70  
  Purchase #3 $244.57   3.318%   $252.6848   $252.68   $252.70   $252.70  
  Purchase #4 $194.60   5.190%   $204.6997   $204.70   $204.70   $204.70  
  Purchase #5 $46.43   5.386%   $48.9307   $48.93   $48.95   $48.90  
  Purchase #6 $86.84   13.839%   $98.8578   $98.86   $98.85   $98.90  
  Purchase #7 $187.98   8.593%   $204.1331   $204.13   $204.15   $204.10  
  7 purchase totals = $1,077.98       $1,163.2554   $1,163.25   $1,163.30   $1,163.30