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 $238.36   12.366%   $267.8356   $267.84   $267.85   $267.80  
  Purchase #2 $205.92   9.691%   $225.8757   $225.88   $225.90   $225.90  
  Purchase #3 $118.45   4.847%   $124.1913   $124.19   $124.20   $124.20  
  Purchase #4 $57.36   11.125%   $63.7413   $63.74   $63.75   $63.70  
  Purchase #5 $71.75   9.543%   $78.5971   $78.60   $78.60   $78.60  
  Purchase #6 $60.96   5.181%   $64.1183   $64.12   $64.10   $64.10  
  Purchase #7 $63.42   11.470%   $70.6943   $70.69   $70.70   $70.70  
  7 purchase totals = $816.22       $895.0536   $895.06   $895.10   $895.00