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 $193.94   8.646%   $210.7081   $210.71   $210.70   $210.70  
  Purchase #2 $62.33   8.853%   $67.8481   $67.85   $67.85   $67.80  
  Purchase #3 $85.42   6.172%   $90.6921   $90.69   $90.70   $90.70  
  Purchase #4 $65.64   12.654%   $73.9461   $73.95   $73.95   $73.90  
  Purchase #5 $202.53   3.676%   $209.975   $209.98   $210.00   $210.00  
  Purchase #6 $58.56   5.328%   $61.6801   $61.68   $61.70   $61.70  
  Purchase #7 $29.26   3.746%   $30.3561   $30.36   $30.35   $30.40  
  7 purchase totals = $697.68       $745.2056   $745.22   $745.25   $745.20