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 $149.81   8.758%   $162.9304   $162.93   $162.95   $162.90  
  Purchase #2 $203.32   6.747%   $217.038   $217.04   $217.05   $217.00  
  Purchase #3 $75.39   6.371%   $80.1931   $80.19   $80.20   $80.20  
  Purchase #4 $235.79   11.229%   $262.2669   $262.27   $262.25   $262.30  
  Purchase #5 $201.36   5.555%   $212.5455   $212.55   $212.55   $212.50  
  Purchase #6 $197.41   4.723%   $206.7337   $206.73   $206.75   $206.70  
  Purchase #7 $67.93   7.814%   $73.2381   $73.24   $73.25   $73.20  
  7 purchase totals = $1,131.01       $1,214.9457   $1,214.95   $1,215.00   $1,214.80