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 $67.63   13.444%   $76.7222   $76.72   $76.70   $76.70  
  Purchase #2 $220.53   12.137%   $247.2957   $247.30   $247.30   $247.30  
  Purchase #3 $50.25   6.286%   $53.4087   $53.41   $53.40   $53.40  
  Purchase #4 $147.89   4.145%   $154.02   $154.02   $154.00   $154.00  
  Purchase #5 $226.67   6.285%   $240.9162   $240.92   $240.90   $240.90  
  Purchase #6 $119.66   12.657%   $134.8054   $134.81   $134.80   $134.80  
  Purchase #7 $197.44   11.697%   $220.5346   $220.53   $220.55   $220.50  
  7 purchase totals = $1,030.07       $1,127.7028   $1,127.71   $1,127.65   $1,127.60