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 $218.43   6.520%   $232.6716   $232.67   $232.65   $232.70  
  Purchase #2 $103.39   12.618%   $116.4358   $116.44   $116.45   $116.40  
  Purchase #3 $55.92   4.799%   $58.6036   $58.60   $58.60   $58.60  
  Purchase #4 $198.44   3.121%   $204.6333   $204.63   $204.65   $204.60  
  Purchase #5 $248.88   4.237%   $259.425   $259.43   $259.45   $259.40  
  Purchase #6 $123.49   7.202%   $132.3837   $132.38   $132.40   $132.40  
  Purchase #7 $51.89   13.406%   $58.8464   $58.85   $58.85   $58.80  
  7 purchase totals = $1,000.44       $1,062.9994   $1,063.00   $1,063.05   $1,062.90