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 $181.97   12.677%   $205.0383   $205.04   $205.05   $205.00  
  Purchase #2 $32.90   6.324%   $34.9806   $34.98   $35.00   $35.00  
  Purchase #3 $212.44   6.804%   $226.8944   $226.89   $226.90   $226.90  
  Purchase #4 $230.34   8.652%   $250.269   $250.27   $250.25   $250.30  
  Purchase #5 $23.34   6.202%   $24.7875   $24.79   $24.80   $24.80  
  Purchase #6 $182.39   3.801%   $189.3226   $189.32   $189.30   $189.30  
  Purchase #7 $158.63   4.212%   $165.3115   $165.31   $165.30   $165.30  
  7 purchase totals = $1,022.01       $1,096.6039   $1,096.60   $1,096.60   $1,096.60