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 $81.77   4.811%   $85.704   $85.70   $85.70   $85.70  
  Purchase #2 $154.83   8.362%   $167.7769   $167.78   $167.80   $167.80  
  Purchase #3 $94.27   7.415%   $101.2601   $101.26   $101.25   $101.30  
  Purchase #4 $58.60   9.735%   $64.3047   $64.30   $64.30   $64.30  
  Purchase #5 $220.85   12.849%   $249.227   $249.23   $249.25   $249.20  
  Purchase #6 $56.29   5.155%   $59.1917   $59.19   $59.20   $59.20  
  Purchase #7 $178.47   11.207%   $198.4711   $198.47   $198.45   $198.50  
  7 purchase totals = $845.08       $925.9355   $925.93   $925.95   $926.00