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 $187.41   7.520%   $201.5032   $201.50   $201.50   $201.50  
  Purchase #2 $31.83   8.703%   $34.6002   $34.60   $34.60   $34.60  
  Purchase #3 $109.42   5.494%   $115.4315   $115.43   $115.45   $115.40  
  Purchase #4 $132.84   13.689%   $151.0245   $151.02   $151.00   $151.00  
  Purchase #5 $73.71   11.165%   $81.9397   $81.94   $81.95   $81.90  
  Purchase #6 $108.36   5.401%   $114.2125   $114.21   $114.20   $114.20  
  Purchase #7 $227.71   6.282%   $242.0147   $242.01   $242.00   $242.00  
  7 purchase totals = $871.28       $940.7263   $940.71   $940.70   $940.60