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 $60.55   11.707%   $67.6386   $67.64   $67.65   $67.60  
  Purchase #2 $180.26   7.521%   $193.8174   $193.82   $193.80   $193.80  
  Purchase #3 $175.36   13.523%   $199.0739   $199.07   $199.05   $199.10  
  Purchase #4 $197.71   5.169%   $207.9296   $207.93   $207.95   $207.90  
  Purchase #5 $75.75   5.703%   $80.07   $80.07   $80.05   $80.10  
  Purchase #6 $163.43   4.817%   $171.3024   $171.30   $171.30   $171.30  
  Purchase #7 $195.36   3.555%   $202.305   $202.31   $202.30   $202.30  
  7 purchase totals = $1,048.42       $1,122.1369   $1,122.14   $1,122.10   $1,122.10