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 $64.26   5.765%   $67.9646   $67.96   $67.95   $68.00  
  Purchase #2 $149.27   8.753%   $162.3356   $162.34   $162.35   $162.30  
  Purchase #3 $28.90   12.158%   $32.4137   $32.41   $32.40   $32.40  
  Purchase #4 $204.42   8.639%   $222.0798   $222.08   $222.10   $222.10  
  Purchase #5 $246.84   7.268%   $264.7803   $264.78   $264.80   $264.80  
  Purchase #6 $185.76   12.103%   $208.2425   $208.24   $208.25   $208.20  
  Purchase #7 $66.88   13.827%   $76.1275   $76.13   $76.15   $76.10  
  7 purchase totals = $946.33       $1,033.9440   $1,033.94   $1,034.00   $1,033.90