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 $92.61   5.318%   $97.535   $97.54   $97.55   $97.50  
  Purchase #2 $250.72   9.578%   $274.734   $274.73   $274.75   $274.70  
  Purchase #3 $71.28   12.183%   $79.964   $79.96   $79.95   $80.00  
  Purchase #4 $171.89   4.536%   $179.6869   $179.69   $179.70   $179.70  
  Purchase #5 $118.35   6.199%   $125.6865   $125.69   $125.70   $125.70  
  Purchase #6 $154.36   5.793%   $163.3021   $163.30   $163.30   $163.30  
  Purchase #7 $99.94   5.831%   $105.7675   $105.77   $105.75   $105.80  
  7 purchase totals = $959.15       $1,026.6760   $1,026.68   $1,026.70   $1,026.70