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 $98.95   8.179%   $107.0431   $107.04   $107.05   $107.00  
  Purchase #2 $182.87   11.584%   $204.0537   $204.05   $204.05   $204.10  
  Purchase #3 $13.61   4.662%   $14.2445   $14.24   $14.25   $14.20  
  Purchase #4 $193.92   12.339%   $217.8478   $217.85   $217.85   $217.80  
  Purchase #5 $227.84   8.527%   $247.2679   $247.27   $247.25   $247.30  
  Purchase #6 $191.58   10.288%   $211.2898   $211.29   $211.30   $211.30  
  Purchase #7 $158.39   9.504%   $173.4434   $173.44   $173.45   $173.40  
  7 purchase totals = $1,067.16       $1,175.1902   $1,175.18   $1,175.20   $1,175.10