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 $208.33   12.449%   $234.265   $234.27   $234.25   $234.30  
  Purchase #2 $203.56   7.543%   $218.9145   $218.91   $218.90   $218.90  
  Purchase #3 $50.36   12.166%   $56.4868   $56.49   $56.50   $56.50  
  Purchase #4 $60.98   13.566%   $69.2525   $69.25   $69.25   $69.30  
  Purchase #5 $178.49   3.501%   $184.7389   $184.74   $184.75   $184.70  
  Purchase #6 $222.80   11.206%   $247.767   $247.77   $247.75   $247.80  
  Purchase #7 $163.91   8.130%   $177.2359   $177.24   $177.25   $177.20  
  7 purchase totals = $1,088.43       $1,188.6606   $1,188.67   $1,188.65   $1,188.70