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 $114.42   7.457%   $122.9523   $122.95   $122.95   $123.00  
  Purchase #2 $206.29   3.784%   $214.096   $214.10   $214.10   $214.10  
  Purchase #3 $155.46   10.514%   $171.8051   $171.81   $171.80   $171.80  
  Purchase #4 $23.33   11.308%   $25.9682   $25.97   $25.95   $26.00  
  Purchase #5 $116.91   9.535%   $128.0574   $128.06   $128.05   $128.10  
  Purchase #6 $163.61   6.840%   $174.8009   $174.80   $174.80   $174.80  
  Purchase #7 $146.37   5.328%   $154.1686   $154.17   $154.15   $154.20  
  7 purchase totals = $926.39       $991.8485   $991.86   $991.80   $992.00