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 $54.78   13.621%   $62.2416   $62.24   $62.25   $62.20  
  Purchase #2 $232.35   4.177%   $242.0553   $242.06   $242.05   $242.10  
  Purchase #3 $158.65   11.232%   $176.4696   $176.47   $176.45   $176.50  
  Purchase #4 $157.25   7.232%   $168.6223   $168.62   $168.60   $168.60  
  Purchase #5 $179.99   10.298%   $198.5254   $198.53   $198.55   $198.50  
  Purchase #6 $11.79   13.609%   $13.3945   $13.39   $13.40   $13.40  
  Purchase #7 $230.48   6.384%   $245.1938   $245.19   $245.20   $245.20  
  7 purchase totals = $1,025.29       $1,106.5025   $1,106.50   $1,106.50   $1,106.50