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 $82.45   13.607%   $93.669   $93.67   $93.65   $93.70  
  Purchase #2 $216.60   8.289%   $234.554   $234.55   $234.55   $234.60  
  Purchase #3 $97.26   5.862%   $102.9614   $102.96   $102.95   $103.00  
  Purchase #4 $152.99   3.741%   $158.7134   $158.71   $158.70   $158.70  
  Purchase #5 $168.28   9.611%   $184.4534   $184.45   $184.45   $184.50  
  Purchase #6 $35.78   8.461%   $38.8073   $38.81   $38.80   $38.80  
  Purchase #7 $200.94   10.781%   $222.6033   $222.60   $222.60   $222.60  
  7 purchase totals = $954.30       $1,035.7618   $1,035.75   $1,035.70   $1,035.90