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 $58.36   6.123%   $61.9334   $61.93   $61.95   $61.90  
  Purchase #2 $107.85   9.640%   $118.2467   $118.25   $118.25   $118.20  
  Purchase #3 $250.80   13.248%   $284.026   $284.03   $284.05   $284.00  
  Purchase #4 $185.76   7.309%   $199.3372   $199.34   $199.35   $199.30  
  Purchase #5 $31.93   13.345%   $36.1911   $36.19   $36.20   $36.20  
  Purchase #6 $88.91   8.705%   $96.6496   $96.65   $96.65   $96.60  
  Purchase #7 $250.48   10.444%   $276.6401   $276.64   $276.65   $276.60  
  7 purchase totals = $974.09       $1,073.0241   $1,073.03   $1,073.10   $1,072.80