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 $59.37   12.260%   $66.6488   $66.65   $66.65   $66.60  
  Purchase #2 $120.41   4.600%   $125.9489   $125.95   $125.95   $125.90  
  Purchase #3 $145.83   4.239%   $152.0117   $152.01   $152.00   $152.00  
  Purchase #4 $113.46   13.299%   $128.549   $128.55   $128.55   $128.50  
  Purchase #5 $151.56   5.225%   $159.479   $159.48   $159.50   $159.50  
  Purchase #6 $206.66   6.796%   $220.7046   $220.70   $220.70   $220.70  
  Purchase #7 $244.69   3.182%   $252.476   $252.48   $252.50   $252.50  
  7 purchase totals = $1,041.98       $1,105.8180   $1,105.82   $1,105.85   $1,105.70