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 $207.36   9.230%   $226.4993   $226.50   $226.50   $226.50  
  Purchase #2 $39.90   9.415%   $43.6566   $43.66   $43.65   $43.70  
  Purchase #3 $184.30   10.830%   $204.2597   $204.26   $204.25   $204.30  
  Purchase #4 $217.85   8.457%   $236.2736   $236.27   $236.25   $236.30  
  Purchase #5 $136.91   12.598%   $154.1579   $154.16   $154.15   $154.20  
  Purchase #6 $51.30   7.712%   $55.2563   $55.26   $55.25   $55.30  
  Purchase #7 $89.31   5.673%   $94.3766   $94.38   $94.40   $94.40  
  7 purchase totals = $926.93       $1,014.4800   $1,014.49   $1,014.45   $1,014.70