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 $23.36   4.709%   $24.46   $24.46   $24.45   $24.50  
  Purchase #2 $236.31   3.676%   $244.9968   $245.00   $245.00   $245.00  
  Purchase #3 $34.99   11.386%   $38.974   $38.97   $38.95   $39.00  
  Purchase #4 $207.59   9.232%   $226.7547   $226.75   $226.75   $226.80  
  Purchase #5 $112.47   7.248%   $120.6218   $120.62   $120.60   $120.60  
  Purchase #6 $247.31   5.519%   $260.959   $260.96   $260.95   $261.00  
  Purchase #7 $176.78   8.511%   $191.8257   $191.83   $191.85   $191.80  
  7 purchase totals = $1,038.81       $1,108.5920   $1,108.59   $1,108.55   $1,108.70