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 $71.38   7.203%   $76.5215   $76.52   $76.50   $76.50  
  Purchase #2 $147.64   4.758%   $154.6647   $154.66   $154.65   $154.70  
  Purchase #3 $212.39   12.639%   $239.234   $239.23   $239.25   $239.20  
  Purchase #4 $8.93   10.442%   $9.8625   $9.86   $9.85   $9.90  
  Purchase #5 $176.52   5.611%   $186.4245   $186.42   $186.40   $186.40  
  Purchase #6 $125.30   13.208%   $141.8496   $141.85   $141.85   $141.80  
  Purchase #7 $217.98   6.764%   $232.7242   $232.72   $232.70   $232.70  
  7 purchase totals = $960.14       $1,041.2810   $1,041.26   $1,041.20   $1,041.20