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 $55.94   11.871%   $62.5806   $62.58   $62.60   $62.60  
  Purchase #2 $217.92   6.361%   $231.7819   $231.78   $231.80   $231.80  
  Purchase #3 $224.70   5.308%   $236.6271   $236.63   $236.65   $236.60  
  Purchase #4 $249.52   5.121%   $262.2979   $262.30   $262.30   $262.30  
  Purchase #5 $211.57   13.539%   $240.2145   $240.21   $240.20   $240.20  
  Purchase #6 $224.77   12.686%   $253.2843   $253.28   $253.30   $253.30  
  Purchase #7 $140.39   5.220%   $147.7184   $147.72   $147.70   $147.70  
  7 purchase totals = $1,324.81       $1,434.5047   $1,434.50   $1,434.55   $1,434.50