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 $58.25   6.499%   $62.0357   $62.04   $62.05   $62.00  
  Purchase #2 $135.78   4.123%   $141.3782   $141.38   $141.40   $141.40  
  Purchase #3 $57.73   10.475%   $63.7772   $63.78   $63.80   $63.80  
  Purchase #4 $209.58   10.513%   $231.6131   $231.61   $231.60   $231.60  
  Purchase #5 $30.98   12.441%   $34.8342   $34.83   $34.85   $34.80  
  Purchase #6 $111.56   3.549%   $115.5193   $115.52   $115.50   $115.50  
  Purchase #7 $101.71   5.370%   $107.1718   $107.17   $107.15   $107.20  
  7 purchase totals = $705.59       $756.3295   $756.33   $756.35   $756.30