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 $33.27   9.805%   $36.5321   $36.53   $36.55   $36.50  
  Purchase #2 $163.76   11.692%   $182.9068   $182.91   $182.90   $182.90  
  Purchase #3 $227.85   7.600%   $245.1666   $245.17   $245.15   $245.20  
  Purchase #4 $180.84   6.281%   $192.1986   $192.20   $192.20   $192.20  
  Purchase #5 $174.74   12.163%   $195.9936   $195.99   $196.00   $196.00  
  Purchase #6 $27.86   4.463%   $29.1034   $29.10   $29.10   $29.10  
  Purchase #7 $151.73   12.865%   $171.2501   $171.25   $171.25   $171.30  
  7 purchase totals = $960.05       $1,053.1512   $1,053.15   $1,053.15   $1,053.20