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 $203.35   5.451%   $214.4346   $214.43   $214.45   $214.40  
  Purchase #2 $174.88   11.663%   $195.2763   $195.28   $195.30   $195.30  
  Purchase #3 $136.87   5.320%   $144.1515   $144.15   $144.15   $144.20  
  Purchase #4 $200.39   3.625%   $207.6541   $207.65   $207.65   $207.70  
  Purchase #5 $230.95   7.146%   $247.4537   $247.45   $247.45   $247.50  
  Purchase #6 $201.66   5.345%   $212.4387   $212.44   $212.45   $212.40  
  Purchase #7 $75.83   5.305%   $79.8528   $79.85   $79.85   $79.90  
  7 purchase totals = $1,223.93       $1,301.2617   $1,301.25   $1,301.30   $1,301.40