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 $207.89   13.340%   $235.6225   $235.62   $235.60   $235.60  
  Purchase #2 $41.55   11.132%   $46.1753   $46.18   $46.20   $46.20  
  Purchase #3 $221.51   4.504%   $231.4868   $231.49   $231.50   $231.50  
  Purchase #4 $63.32   11.224%   $70.427   $70.43   $70.45   $70.40  
  Purchase #5 $65.82   7.485%   $70.7466   $70.75   $70.75   $70.70  
  Purchase #6 $127.37   10.499%   $140.7426   $140.74   $140.75   $140.70  
  Purchase #7 $150.33   4.693%   $157.385   $157.39   $157.40   $157.40  
  7 purchase totals = $877.79       $952.5858   $952.60   $952.65   $952.50