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 $119.44   5.207%   $125.6592   $125.66   $125.65   $125.70  
  Purchase #2 $214.69   8.254%   $232.4105   $232.41   $232.40   $232.40  
  Purchase #3 $46.60   5.552%   $49.1872   $49.19   $49.20   $49.20  
  Purchase #4 $20.53   5.807%   $21.7222   $21.72   $21.70   $21.70  
  Purchase #5 $157.40   6.412%   $167.4925   $167.49   $167.50   $167.50  
  Purchase #6 $155.45   7.774%   $167.5347   $167.53   $167.55   $167.50  
  Purchase #7 $152.49   5.150%   $160.3432   $160.34   $160.35   $160.30  
  7 purchase totals = $866.60       $924.3495   $924.34   $924.35   $924.30