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 $86.28   10.671%   $95.4869   $95.49   $95.50   $95.50  
  Purchase #2 $131.29   11.521%   $146.4159   $146.42   $146.40   $146.40  
  Purchase #3 $118.43   6.218%   $125.794   $125.79   $125.80   $125.80  
  Purchase #4 $202.42   12.413%   $227.5464   $227.55   $227.55   $227.50  
  Purchase #5 $224.93   9.249%   $245.7338   $245.73   $245.75   $245.70  
  Purchase #6 $239.29   11.202%   $266.0953   $266.10   $266.10   $266.10  
  Purchase #7 $40.28   7.261%   $43.2047   $43.20   $43.20   $43.20  
  7 purchase totals = $1,042.92       $1,150.2770   $1,150.28   $1,150.30   $1,150.20