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 $208.51   3.257%   $215.3012   $215.30   $215.30   $215.30  
  Purchase #2 $234.71   9.794%   $257.6975   $257.70   $257.70   $257.70  
  Purchase #3 $124.46   8.183%   $134.6446   $134.64   $134.65   $134.60  
  Purchase #4 $47.80   3.205%   $49.332   $49.33   $49.35   $49.30  
  Purchase #5 $233.45   11.337%   $259.9162   $259.92   $259.90   $259.90  
  Purchase #6 $197.84   3.479%   $204.7229   $204.72   $204.70   $204.70  
  Purchase #7 $150.92   13.546%   $171.3636   $171.36   $171.35   $171.40  
  7 purchase totals = $1,197.69       $1,292.9780   $1,292.97   $1,292.95   $1,292.90