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 $92.88   3.116%   $95.7741   $95.77   $95.75   $95.80  
  Purchase #2 $155.29   6.348%   $165.1478   $165.15   $165.15   $165.10  
  Purchase #3 $218.66   5.272%   $230.1878   $230.19   $230.20   $230.20  
  Purchase #4 $164.45   8.708%   $178.7703   $178.77   $178.75   $178.80  
  Purchase #5 $146.61   9.872%   $161.0833   $161.08   $161.10   $161.10  
  Purchase #6 $57.67   6.324%   $61.3171   $61.32   $61.30   $61.30  
  Purchase #7 $66.26   5.722%   $70.0514   $70.05   $70.05   $70.10  
  7 purchase totals = $901.82       $962.3318   $962.33   $962.30   $962.40