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 $167.49   4.868%   $175.6434   $175.64   $175.65   $175.60  
  Purchase #2 $54.48   4.619%   $56.9964   $57.00   $57.00   $57.00  
  Purchase #3 $153.44   13.584%   $174.2833   $174.28   $174.30   $174.30  
  Purchase #4 $236.57   7.659%   $254.6889   $254.69   $254.70   $254.70  
  Purchase #5 $21.66   9.274%   $23.6687   $23.67   $23.65   $23.70  
  Purchase #6 $188.27   8.295%   $203.887   $203.89   $203.90   $203.90  
  Purchase #7 $237.30   12.824%   $267.7314   $267.73   $267.75   $267.70  
  7 purchase totals = $1,059.21       $1,156.8991   $1,156.90   $1,156.95   $1,156.90