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 $161.96   5.774%   $171.3116   $171.31   $171.30   $171.30  
  Purchase #2 $174.79   3.691%   $181.2415   $181.24   $181.25   $181.20  
  Purchase #3 $17.83   8.551%   $19.3546   $19.35   $19.35   $19.40  
  Purchase #4 $91.41   4.824%   $95.8196   $95.82   $95.80   $95.80  
  Purchase #5 $40.41   13.741%   $45.9627   $45.96   $45.95   $46.00  
  Purchase #6 $41.38   12.462%   $46.5368   $46.54   $46.55   $46.50  
  Purchase #7 $174.73   13.759%   $198.7711   $198.77   $198.75   $198.80  
  7 purchase totals = $702.51       $758.9979   $758.99   $758.95   $759.00