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 $41.41   5.291%   $43.601   $43.60   $43.60   $43.60  
  Purchase #2 $116.35   10.107%   $128.1095   $128.11   $128.10   $128.10  
  Purchase #3 $186.75   9.710%   $204.8834   $204.88   $204.90   $204.90  
  Purchase #4 $152.64   3.301%   $157.6786   $157.68   $157.70   $157.70  
  Purchase #5 $192.25   7.622%   $206.9033   $206.90   $206.90   $206.90  
  Purchase #6 $185.59   8.653%   $201.6491   $201.65   $201.65   $201.60  
  Purchase #7 $92.45   13.221%   $104.6728   $104.67   $104.65   $104.70  
  7 purchase totals = $967.44       $1,047.4977   $1,047.49   $1,047.50   $1,047.50