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 $120.89   4.661%   $126.5247   $126.52   $126.50   $126.50  
  Purchase #2 $22.33   11.752%   $24.9542   $24.95   $24.95   $25.00  
  Purchase #3 $249.33   6.499%   $265.534   $265.53   $265.55   $265.50  
  Purchase #4 $134.69   10.479%   $148.8042   $148.80   $148.80   $148.80  
  Purchase #5 $196.41   4.158%   $204.5767   $204.58   $204.60   $204.60  
  Purchase #6 $191.42   7.445%   $205.6712   $205.67   $205.65   $205.70  
  Purchase #7 $86.97   7.682%   $93.651   $93.65   $93.65   $93.70  
  7 purchase totals = $1,002.04       $1,069.7160   $1,069.70   $1,069.70   $1,069.80