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 $227.89   10.597%   $252.0395   $252.04   $252.05   $252.00  
  Purchase #2 $212.96   6.327%   $226.434   $226.43   $226.45   $226.40  
  Purchase #3 $11.88   6.377%   $12.6376   $12.64   $12.65   $12.60  
  Purchase #4 $16.36   3.464%   $16.9267   $16.93   $16.95   $16.90  
  Purchase #5 $113.43   11.630%   $126.6219   $126.62   $126.60   $126.60  
  Purchase #6 $215.68   3.743%   $223.7529   $223.75   $223.75   $223.80  
  Purchase #7 $237.61   6.447%   $252.9287   $252.93   $252.95   $252.90  
  7 purchase totals = $1,035.81       $1,111.3413   $1,111.34   $1,111.40   $1,111.20