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 $71.65   7.370%   $76.9306   $76.93   $76.95   $76.90  
  Purchase #2 $196.55   11.842%   $219.8255   $219.83   $219.85   $219.80  
  Purchase #3 $155.33   9.811%   $170.5694   $170.57   $170.55   $170.60  
  Purchase #4 $83.43   13.679%   $94.8424   $94.84   $94.85   $94.80  
  Purchase #5 $24.87   6.365%   $26.453   $26.45   $26.45   $26.50  
  Purchase #6 $162.81   9.756%   $178.6937   $178.69   $178.70   $178.70  
  Purchase #7 $88.89   10.657%   $98.363   $98.36   $98.35   $98.40  
  7 purchase totals = $783.53       $865.6776   $865.67   $865.70   $865.70