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 $141.68   5.329%   $149.2301   $149.23   $149.25   $149.20  
  Purchase #2 $186.65   4.405%   $194.8719   $194.87   $194.85   $194.90  
  Purchase #3 $199.36   6.582%   $212.4819   $212.48   $212.50   $212.50  
  Purchase #4 $178.26   5.589%   $188.223   $188.22   $188.20   $188.20  
  Purchase #5 $100.58   5.358%   $105.9691   $105.97   $105.95   $106.00  
  Purchase #6 $150.54   4.582%   $157.4377   $157.44   $157.45   $157.40  
  Purchase #7 $25.28   5.712%   $26.724   $26.72   $26.70   $26.70  
  7 purchase totals = $982.35       $1,034.9377   $1,034.93   $1,034.90   $1,034.90