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 $71.32   6.761%   $76.1419   $76.14   $76.15   $76.10  
  Purchase #2 $198.38   3.467%   $205.2578   $205.26   $205.25   $205.30  
  Purchase #3 $219.75   7.357%   $235.917   $235.92   $235.90   $235.90  
  Purchase #4 $137.61   10.511%   $152.0742   $152.07   $152.05   $152.10  
  Purchase #5 $135.28   13.152%   $153.072   $153.07   $153.05   $153.10  
  Purchase #6 $157.36   10.342%   $173.6342   $173.63   $173.65   $173.60  
  Purchase #7 $182.49   3.828%   $189.4757   $189.48   $189.50   $189.50  
  7 purchase totals = $1,102.19       $1,185.5728   $1,185.57   $1,185.55   $1,185.60