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 $68.58   10.803%   $75.9887   $75.99   $76.00   $76.00  
  Purchase #2 $187.87   4.471%   $196.2697   $196.27   $196.25   $196.30  
  Purchase #3 $66.53   7.638%   $71.6116   $71.61   $71.60   $71.60  
  Purchase #4 $107.52   5.320%   $113.2401   $113.24   $113.25   $113.20  
  Purchase #5 $147.77   6.148%   $156.8549   $156.85   $156.85   $156.90  
  Purchase #6 $178.98   13.295%   $202.7754   $202.78   $202.80   $202.80  
  Purchase #7 $241.54   13.719%   $274.6769   $274.68   $274.70   $274.70  
  7 purchase totals = $998.79       $1,091.4173   $1,091.42   $1,091.45   $1,091.50