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 $223.27   4.714%   $233.7949   $233.79   $233.80   $233.80  
  Purchase #2 $174.44   13.337%   $197.7051   $197.71   $197.70   $197.70  
  Purchase #3 $180.48   7.254%   $193.572   $193.57   $193.55   $193.60  
  Purchase #4 $98.86   5.792%   $104.586   $104.59   $104.60   $104.60  
  Purchase #5 $227.38   7.452%   $244.3244   $244.32   $244.30   $244.30  
  Purchase #6 $170.39   7.546%   $183.2476   $183.25   $183.25   $183.20  
  Purchase #7 $218.67   3.818%   $227.0188   $227.02   $227.00   $227.00  
  7 purchase totals = $1,293.49       $1,384.2488   $1,384.25   $1,384.20   $1,384.20