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 $84.44   13.372%   $95.7313   $95.73   $95.75   $95.70  
  Purchase #2 $200.44   8.143%   $216.7618   $216.76   $216.75   $216.80  
  Purchase #3 $191.69   8.556%   $208.091   $208.09   $208.10   $208.10  
  Purchase #4 $187.30   8.196%   $202.6511   $202.65   $202.65   $202.70  
  Purchase #5 $59.31   5.427%   $62.5288   $62.53   $62.55   $62.50  
  Purchase #6 $211.76   7.777%   $228.2286   $228.23   $228.25   $228.20  
  Purchase #7 $223.48   6.471%   $237.9414   $237.94   $237.95   $237.90  
  7 purchase totals = $1,158.42       $1,251.9340   $1,251.93   $1,252.00   $1,251.90