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 $58.55   11.199%   $65.107   $65.11   $65.10   $65.10  
  Purchase #2 $157.38   3.540%   $162.9513   $162.95   $162.95   $163.00  
  Purchase #3 $37.45   3.512%   $38.7652   $38.77   $38.75   $38.80  
  Purchase #4 $214.98   9.647%   $235.7191   $235.72   $235.70   $235.70  
  Purchase #5 $126.34   11.757%   $141.1938   $141.19   $141.20   $141.20  
  Purchase #6 $242.91   13.814%   $276.4656   $276.47   $276.45   $276.50  
  Purchase #7 $233.98   13.874%   $266.4424   $266.44   $266.45   $266.40  
  7 purchase totals = $1,071.59       $1,186.6444   $1,186.65   $1,186.60   $1,186.70