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 $88.69   10.214%   $97.7488   $97.75   $97.75   $97.70  
  Purchase #2 $29.88   7.218%   $32.0367   $32.04   $32.05   $32.00  
  Purchase #3 $171.86   4.574%   $179.7209   $179.72   $179.70   $179.70  
  Purchase #4 $221.78   10.812%   $245.7589   $245.76   $245.75   $245.80  
  Purchase #5 $161.35   11.343%   $179.6519   $179.65   $179.65   $179.70  
  Purchase #6 $248.25   11.858%   $277.6875   $277.69   $277.70   $277.70  
  Purchase #7 $186.57   4.810%   $195.544   $195.54   $195.55   $195.50  
  7 purchase totals = $1,108.38       $1,208.1487   $1,208.15   $1,208.15   $1,208.10