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 $91.59   3.703%   $94.9816   $94.98   $95.00   $95.00  
  Purchase #2 $115.38   8.321%   $124.9808   $124.98   $125.00   $125.00  
  Purchase #3 $170.77   4.545%   $178.5315   $178.53   $178.55   $178.50  
  Purchase #4 $118.82   9.533%   $130.1471   $130.15   $130.15   $130.10  
  Purchase #5 $8.32   3.375%   $8.6008   $8.60   $8.60   $8.60  
  Purchase #6 $240.75   9.247%   $263.0122   $263.01   $263.00   $263.00  
  Purchase #7 $54.93   6.393%   $58.4417   $58.44   $58.45   $58.40  
  7 purchase totals = $800.56       $858.6957   $858.69   $858.75   $858.60