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 $10.93   5.587%   $11.5407   $11.54   $11.55   $11.50  
  Purchase #2 $198.51   5.578%   $209.5829   $209.58   $209.60   $209.60  
  Purchase #3 $179.81   8.642%   $195.3492   $195.35   $195.35   $195.30  
  Purchase #4 $114.33   11.813%   $127.8358   $127.84   $127.85   $127.80  
  Purchase #5 $165.87   5.613%   $175.1803   $175.18   $175.20   $175.20  
  Purchase #6 $160.86   13.247%   $182.1691   $182.17   $182.15   $182.20  
  Purchase #7 $202.31   3.130%   $208.6423   $208.64   $208.65   $208.60  
  7 purchase totals = $1,032.62       $1,110.3003   $1,110.30   $1,110.35   $1,110.20