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 $216.68   8.767%   $235.6763   $235.68   $235.70   $235.70  
  Purchase #2 $239.70   11.548%   $267.3806   $267.38   $267.40   $267.40  
  Purchase #3 $95.59   11.504%   $106.5867   $106.59   $106.60   $106.60  
  Purchase #4 $184.28   8.505%   $199.953   $199.95   $199.95   $200.00  
  Purchase #5 $117.67   6.356%   $125.1491   $125.15   $125.15   $125.10  
  Purchase #6 $114.85   8.253%   $124.3286   $124.33   $124.35   $124.30  
  Purchase #7 $14.65   3.429%   $15.1523   $15.15   $15.15   $15.20  
  7 purchase totals = $983.42       $1,074.2266   $1,074.23   $1,074.30   $1,074.30