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 $67.71   6.843%   $72.3434   $72.34   $72.35   $72.30  
  Purchase #2 $220.74   7.134%   $236.4876   $236.49   $236.50   $236.50  
  Purchase #3 $184.40   3.294%   $190.4741   $190.47   $190.45   $190.50  
  Purchase #4 $152.84   6.179%   $162.284   $162.28   $162.30   $162.30  
  Purchase #5 $15.87   9.849%   $17.433   $17.43   $17.45   $17.40  
  Purchase #6 $152.90   4.693%   $160.0756   $160.08   $160.10   $160.10  
  Purchase #7 $175.61   10.472%   $193.9999   $194.00   $194.00   $194.00  
  7 purchase totals = $970.07       $1,033.0976   $1,033.09   $1,033.15   $1,033.10