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 $194.94   3.353%   $201.4763   $201.48   $201.50   $201.50  
  Purchase #2 $234.66   3.392%   $242.6197   $242.62   $242.60   $242.60  
  Purchase #3 $13.96   7.536%   $15.012   $15.01   $15.00   $15.00  
  Purchase #4 $164.61   4.408%   $171.866   $171.87   $171.85   $171.90  
  Purchase #5 $180.50   8.355%   $195.5808   $195.58   $195.60   $195.60  
  Purchase #6 $120.91   12.699%   $136.2644   $136.26   $136.25   $136.30  
  Purchase #7 $123.98   6.840%   $132.4602   $132.46   $132.45   $132.50  
  7 purchase totals = $1,033.56       $1,095.2794   $1,095.28   $1,095.25   $1,095.40