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 $58.80   5.431%   $61.9934   $61.99   $62.00   $62.00  
  Purchase #2 $176.27   12.283%   $197.9212   $197.92   $197.90   $197.90  
  Purchase #3 $237.33   6.809%   $253.4898   $253.49   $253.50   $253.50  
  Purchase #4 $146.61   3.537%   $151.7956   $151.80   $151.80   $151.80  
  Purchase #5 $208.63   12.610%   $234.9382   $234.94   $234.95   $234.90  
  Purchase #6 $194.80   8.417%   $211.1963   $211.20   $211.20   $211.20  
  Purchase #7 $218.51   5.227%   $229.9315   $229.93   $229.95   $229.90  
  7 purchase totals = $1,240.95       $1,341.2660   $1,341.27   $1,341.30   $1,341.20