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 $184.34   11.723%   $205.9502   $205.95   $205.95   $206.00  
  Purchase #2 $201.34   3.603%   $208.5943   $208.59   $208.60   $208.60  
  Purchase #3 $10.74   8.575%   $11.661   $11.66   $11.65   $11.70  
  Purchase #4 $110.45   4.718%   $115.661   $115.66   $115.65   $115.70  
  Purchase #5 $39.82   3.519%   $41.2213   $41.22   $41.20   $41.20  
  Purchase #6 $44.90   8.185%   $48.5751   $48.58   $48.60   $48.60  
  Purchase #7 $71.62   5.729%   $75.7231   $75.72   $75.70   $75.70  
  7 purchase totals = $663.21       $707.3860   $707.38   $707.35   $707.50