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 $58.84   4.708%   $61.6102   $61.61   $61.60   $61.60  
  Purchase #2 $69.43   11.129%   $77.1569   $77.16   $77.15   $77.20  
  Purchase #3 $97.84   8.288%   $105.949   $105.95   $105.95   $105.90  
  Purchase #4 $179.83   11.839%   $201.1201   $201.12   $201.10   $201.10  
  Purchase #5 $209.67   11.341%   $233.4487   $233.45   $233.45   $233.40  
  Purchase #6 $209.77   4.797%   $219.8327   $219.83   $219.85   $219.80  
  Purchase #7 $125.30   13.202%   $141.8421   $141.84   $141.85   $141.80  
  7 purchase totals = $950.68       $1,040.9597   $1,040.96   $1,040.95   $1,040.80