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 $205.41   10.486%   $226.9493   $226.95   $226.95   $226.90  
  Purchase #2 $246.36   5.405%   $259.6758   $259.68   $259.70   $259.70  
  Purchase #3 $204.32   5.274%   $215.0958   $215.10   $215.10   $215.10  
  Purchase #4 $190.86   9.545%   $209.0776   $209.08   $209.10   $209.10  
  Purchase #5 $89.31   3.627%   $92.5493   $92.55   $92.55   $92.50  
  Purchase #6 $48.87   7.239%   $52.4077   $52.41   $52.40   $52.40  
  Purchase #7 $7.65   4.224%   $7.9731   $7.97   $7.95   $8.00  
  7 purchase totals = $992.78       $1,063.7286   $1,063.74   $1,063.75   $1,063.70