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 $105.41   13.704%   $119.8554   $119.86   $119.85   $119.90  
  Purchase #2 $166.35   10.720%   $184.1827   $184.18   $184.20   $184.20  
  Purchase #3 $10.32   11.739%   $11.5315   $11.53   $11.55   $11.50  
  Purchase #4 $144.78   13.646%   $164.5367   $164.54   $164.55   $164.50  
  Purchase #5 $147.52   8.752%   $160.431   $160.43   $160.45   $160.40  
  Purchase #6 $58.43   11.123%   $64.9292   $64.93   $64.95   $64.90  
  Purchase #7 $161.83   8.785%   $176.0468   $176.05   $176.05   $176.00  
  7 purchase totals = $794.64       $881.5133   $881.52   $881.60   $881.40