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 $33.26   4.343%   $34.7045   $34.70   $34.70   $34.70  
  Purchase #2 $26.83   8.459%   $29.0995   $29.10   $29.10   $29.10  
  Purchase #3 $189.29   4.762%   $198.304   $198.30   $198.30   $198.30  
  Purchase #4 $86.43   9.216%   $94.3954   $94.40   $94.40   $94.40  
  Purchase #5 $230.89   4.859%   $242.1089   $242.11   $242.10   $242.10  
  Purchase #6 $123.76   13.107%   $139.9812   $139.98   $140.00   $140.00  
  Purchase #7 $199.43   8.285%   $215.9528   $215.95   $215.95   $216.00  
  7 purchase totals = $889.89       $954.5463   $954.54   $954.55   $954.60