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 $62.26   9.462%   $68.151   $68.15   $68.15   $68.20  
  Purchase #2 $53.48   5.707%   $56.5321   $56.53   $56.55   $56.50  
  Purchase #3 $94.49   6.434%   $100.5695   $100.57   $100.55   $100.60  
  Purchase #4 $243.88   8.228%   $263.9464   $263.95   $263.95   $263.90  
  Purchase #5 $172.54   12.667%   $194.3956   $194.40   $194.40   $194.40  
  Purchase #6 $113.48   8.371%   $122.9794   $122.98   $123.00   $123.00  
  Purchase #7 $176.80   6.378%   $188.0763   $188.08   $188.10   $188.10  
  7 purchase totals = $916.93       $994.6503   $994.66   $994.70   $994.70