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 $88.92   6.158%   $94.3957   $94.40   $94.40   $94.40  
  Purchase #2 $246.51   9.413%   $269.714   $269.71   $269.70   $269.70  
  Purchase #3 $77.88   4.796%   $81.6151   $81.62   $81.60   $81.60  
  Purchase #4 $244.54   9.738%   $268.3533   $268.35   $268.35   $268.40  
  Purchase #5 $199.63   8.135%   $215.8699   $215.87   $215.85   $215.90  
  Purchase #6 $48.99   6.248%   $52.0509   $52.05   $52.05   $52.10  
  Purchase #7 $120.50   8.175%   $130.3509   $130.35   $130.35   $130.40  
  7 purchase totals = $1,026.97       $1,112.3498   $1,112.35   $1,112.30   $1,112.50