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 $204.57   10.559%   $226.1705   $226.17   $226.15   $226.20  
  Purchase #2 $166.70   12.368%   $187.3175   $187.32   $187.30   $187.30  
  Purchase #3 $59.80   6.638%   $63.7695   $63.77   $63.75   $63.80  
  Purchase #4 $202.71   3.433%   $209.669   $209.67   $209.65   $209.70  
  Purchase #5 $52.30   6.316%   $55.6033   $55.60   $55.60   $55.60  
  Purchase #6 $193.87   6.373%   $206.2253   $206.23   $206.25   $206.20  
  Purchase #7 $169.56   9.788%   $186.1565   $186.16   $186.15   $186.20  
  7 purchase totals = $1,049.51       $1,134.9116   $1,134.92   $1,134.85   $1,135.00