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 $41.75   12.263%   $46.8698   $46.87   $46.85   $46.90  
  Purchase #2 $206.89   13.813%   $235.4677   $235.47   $235.45   $235.50  
  Purchase #3 $165.35   5.420%   $174.312   $174.31   $174.30   $174.30  
  Purchase #4 $175.90   7.651%   $189.3581   $189.36   $189.35   $189.40  
  Purchase #5 $105.81   12.812%   $119.3664   $119.37   $119.35   $119.40  
  Purchase #6 $190.79   12.533%   $214.7017   $214.70   $214.70   $214.70  
  Purchase #7 $168.54   12.607%   $189.7878   $189.79   $189.80   $189.80  
  7 purchase totals = $1,055.03       $1,169.8635   $1,169.87   $1,169.80   $1,170.00