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 $193.94   3.871%   $201.4474   $201.45   $201.45   $201.40  
  Purchase #2 $249.81   12.806%   $281.8007   $281.80   $281.80   $281.80  
  Purchase #3 $56.92   9.382%   $62.2602   $62.26   $62.25   $62.30  
  Purchase #4 $234.72   8.390%   $254.413   $254.41   $254.40   $254.40  
  Purchase #5 $192.38   6.150%   $204.2114   $204.21   $204.20   $204.20  
  Purchase #6 $230.53   6.551%   $245.632   $245.63   $245.65   $245.60  
  Purchase #7 $233.29   4.381%   $243.5104   $243.51   $243.50   $243.50  
  7 purchase totals = $1,391.59       $1,493.2751   $1,493.27   $1,493.25   $1,493.20