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 $87.50   10.578%   $96.7558   $96.76   $96.75   $96.80  
  Purchase #2 $231.47   9.168%   $252.6912   $252.69   $252.70   $252.70  
  Purchase #3 $72.98   12.807%   $82.3265   $82.33   $82.35   $82.30  
  Purchase #4 $166.33   7.163%   $178.2442   $178.24   $178.25   $178.20  
  Purchase #5 $235.28   13.692%   $267.4945   $267.49   $267.50   $267.50  
  Purchase #6 $94.43   6.166%   $100.2526   $100.25   $100.25   $100.30  
  Purchase #7 $218.55   4.499%   $228.3826   $228.38   $228.40   $228.40  
  7 purchase totals = $1,106.54       $1,206.1474   $1,206.14   $1,206.20   $1,206.20