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 $61.55   3.171%   $63.5018   $63.50   $63.50   $63.50  
  Purchase #2 $211.59   12.366%   $237.7552   $237.76   $237.75   $237.80  
  Purchase #3 $90.37   3.184%   $93.2474   $93.25   $93.25   $93.20  
  Purchase #4 $207.76   3.313%   $214.6431   $214.64   $214.65   $214.60  
  Purchase #5 $218.87   3.776%   $227.1345   $227.13   $227.15   $227.10  
  Purchase #6 $55.31   4.628%   $57.8697   $57.87   $57.85   $57.90  
  Purchase #7 $153.73   13.306%   $174.1853   $174.19   $174.20   $174.20  
  7 purchase totals = $999.18       $1,068.3370   $1,068.34   $1,068.35   $1,068.30