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 $88.80   8.567%   $96.4075   $96.41   $96.40   $96.40  
  Purchase #2 $241.34   4.543%   $252.3041   $252.30   $252.30   $252.30  
  Purchase #3 $153.70   13.258%   $174.0775   $174.08   $174.10   $174.10  
  Purchase #4 $227.87   11.329%   $253.6854   $253.69   $253.70   $253.70  
  Purchase #5 $211.67   10.754%   $234.433   $234.43   $234.45   $234.40  
  Purchase #6 $243.72   9.238%   $266.2349   $266.23   $266.25   $266.20  
  Purchase #7 $34.98   3.570%   $36.2288   $36.23   $36.25   $36.20  
  7 purchase totals = $1,202.08       $1,313.3712   $1,313.37   $1,313.45   $1,313.30