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 $71.38   7.254%   $76.5579   $76.56   $76.55   $76.60  
  Purchase #2 $182.38   8.236%   $197.4008   $197.40   $197.40   $197.40  
  Purchase #3 $191.36   5.446%   $201.7815   $201.78   $201.80   $201.80  
  Purchase #4 $88.81   3.490%   $91.9095   $91.91   $91.90   $91.90  
  Purchase #5 $228.31   3.335%   $235.9241   $235.92   $235.90   $235.90  
  Purchase #6 $147.74   4.201%   $153.9466   $153.95   $153.95   $153.90  
  Purchase #7 $165.40   5.129%   $173.8834   $173.88   $173.90   $173.90  
  7 purchase totals = $1,075.38       $1,131.4038   $1,131.40   $1,131.40   $1,131.40