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 $113.99   4.482%   $119.099   $119.10   $119.10   $119.10  
  Purchase #2 $150.33   4.256%   $156.728   $156.73   $156.75   $156.70  
  Purchase #3 $123.89   8.779%   $134.7663   $134.77   $134.75   $134.80  
  Purchase #4 $203.54   12.514%   $229.011   $229.01   $229.00   $229.00  
  Purchase #5 $228.69   10.328%   $252.3091   $252.31   $252.30   $252.30  
  Purchase #6 $186.96   13.778%   $212.7193   $212.72   $212.70   $212.70  
  Purchase #7 $226.58   9.355%   $247.7766   $247.78   $247.80   $247.80  
  7 purchase totals = $1,233.98       $1,352.4093   $1,352.42   $1,352.40   $1,352.40