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 $95.59   11.488%   $106.5714   $106.57   $106.55   $106.60  
  Purchase #2 $186.62   9.135%   $203.6677   $203.67   $203.65   $203.70  
  Purchase #3 $214.25   8.213%   $231.8464   $231.85   $231.85   $231.80  
  Purchase #4 $66.55   12.757%   $75.0398   $75.04   $75.05   $75.00  
  Purchase #5 $240.67   4.158%   $250.6771   $250.68   $250.70   $250.70  
  Purchase #6 $211.52   8.505%   $229.5098   $229.51   $229.50   $229.50  
  Purchase #7 $50.34   8.355%   $54.5459   $54.55   $54.55   $54.50  
  7 purchase totals = $1,065.54       $1,151.8581   $1,151.87   $1,151.85   $1,151.80