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 $241.93   8.537%   $262.5836   $262.58   $262.60   $262.60  
  Purchase #2 $118.73   12.822%   $133.9536   $133.95   $133.95   $134.00  
  Purchase #3 $156.97   7.326%   $168.4696   $168.47   $168.45   $168.50  
  Purchase #4 $245.68   7.665%   $264.5114   $264.51   $264.50   $264.50  
  Purchase #5 $184.70   6.659%   $196.9992   $197.00   $197.00   $197.00  
  Purchase #6 $44.85   10.502%   $49.5601   $49.56   $49.55   $49.60  
  Purchase #7 $30.82   10.751%   $34.1335   $34.13   $34.15   $34.10  
  7 purchase totals = $1,023.68       $1,110.2110   $1,110.20   $1,110.20   $1,110.30