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 $32.72   11.703%   $36.5492   $36.55   $36.55   $36.50  
  Purchase #2 $185.27   6.130%   $196.6271   $196.63   $196.65   $196.60  
  Purchase #3 $116.99   3.640%   $121.2484   $121.25   $121.25   $121.20  
  Purchase #4 $217.67   10.269%   $240.0225   $240.02   $240.00   $240.00  
  Purchase #5 $222.38   9.269%   $242.9924   $242.99   $243.00   $243.00  
  Purchase #6 $74.55   13.413%   $84.5494   $84.55   $84.55   $84.50  
  Purchase #7 $171.86   7.269%   $184.3525   $184.35   $184.35   $184.40  
  7 purchase totals = $1,021.44       $1,106.3415   $1,106.34   $1,106.35   $1,106.20