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 $216.66   9.856%   $238.014   $238.01   $238.00   $238.00  
  Purchase #2 $69.38   8.329%   $75.1587   $75.16   $75.15   $75.20  
  Purchase #3 $225.27   11.751%   $251.7415   $251.74   $251.75   $251.70  
  Purchase #4 $126.49   8.745%   $137.5516   $137.55   $137.55   $137.60  
  Purchase #5 $45.87   10.508%   $50.69   $50.69   $50.70   $50.70  
  Purchase #6 $200.94   6.139%   $213.2757   $213.28   $213.30   $213.30  
  Purchase #7 $193.69   6.331%   $205.9525   $205.95   $205.95   $206.00  
  7 purchase totals = $1,078.30       $1,172.3840   $1,172.38   $1,172.40   $1,172.50