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 $182.92   5.852%   $193.6245   $193.62   $193.60   $193.60  
  Purchase #2 $47.62   8.138%   $51.4953   $51.50   $51.50   $51.50  
  Purchase #3 $169.86   13.407%   $192.6331   $192.63   $192.65   $192.60  
  Purchase #4 $180.25   7.303%   $193.4137   $193.41   $193.40   $193.40  
  Purchase #5 $58.26   5.600%   $61.5226   $61.52   $61.50   $61.50  
  Purchase #6 $42.37   12.220%   $47.5476   $47.55   $47.55   $47.50  
  Purchase #7 $178.99   12.141%   $200.7212   $200.72   $200.70   $200.70  
  7 purchase totals = $860.27       $940.9580   $940.95   $940.90   $940.80