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 $66.25   6.809%   $70.761   $70.76   $70.75   $70.80  
  Purchase #2 $92.68   11.774%   $103.5921   $103.59   $103.60   $103.60  
  Purchase #3 $169.93   3.174%   $175.3236   $175.32   $175.30   $175.30  
  Purchase #4 $182.79   5.440%   $192.7338   $192.73   $192.75   $192.70  
  Purchase #5 $212.86   5.601%   $224.7823   $224.78   $224.80   $224.80  
  Purchase #6 $54.28   3.691%   $56.2835   $56.28   $56.30   $56.30  
  Purchase #7 $116.28   10.778%   $128.8127   $128.81   $128.80   $128.80  
  7 purchase totals = $895.07       $952.2890   $952.27   $952.30   $952.30