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 $195.82   4.704%   $205.0314   $205.03   $205.05   $205.00  
  Purchase #2 $48.57   6.867%   $51.9053   $51.91   $51.90   $51.90  
  Purchase #3 $156.69   7.557%   $168.5311   $168.53   $168.55   $168.50  
  Purchase #4 $188.27   12.386%   $211.5891   $211.59   $211.60   $211.60  
  Purchase #5 $43.45   8.161%   $46.996   $47.00   $47.00   $47.00  
  Purchase #6 $86.73   11.591%   $96.7829   $96.78   $96.80   $96.80  
  Purchase #7 $154.48   10.835%   $171.2179   $171.22   $171.20   $171.20  
  7 purchase totals = $874.01       $952.0537   $952.06   $952.10   $952.00