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 $39.44   10.503%   $43.5824   $43.58   $43.60   $43.60  
  Purchase #2 $233.71   7.336%   $250.855   $250.86   $250.85   $250.90  
  Purchase #3 $104.32   8.868%   $113.5711   $113.57   $113.55   $113.60  
  Purchase #4 $179.84   6.669%   $191.8335   $191.83   $191.85   $191.80  
  Purchase #5 $204.95   6.230%   $217.7184   $217.72   $217.70   $217.70  
  Purchase #6 $229.28   6.342%   $243.8209   $243.82   $243.80   $243.80  
  Purchase #7 $190.42   7.116%   $203.9703   $203.97   $203.95   $204.00  
  7 purchase totals = $1,181.96       $1,265.3516   $1,265.35   $1,265.30   $1,265.40