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 $174.56   11.722%   $195.0219   $195.02   $195.00   $195.00  
  Purchase #2 $113.26   11.813%   $126.6394   $126.64   $126.65   $126.60  
  Purchase #3 $47.95   12.226%   $53.8124   $53.81   $53.80   $53.80  
  Purchase #4 $37.26   6.478%   $39.6737   $39.67   $39.65   $39.70  
  Purchase #5 $146.50   10.261%   $161.5324   $161.53   $161.55   $161.50  
  Purchase #6 $119.74   3.175%   $123.5417   $123.54   $123.55   $123.50  
  Purchase #7 $25.61   8.398%   $27.7607   $27.76   $27.75   $27.80  
  7 purchase totals = $664.88       $727.9822   $727.97   $727.95   $727.90