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 $32.42   13.248%   $36.715   $36.72   $36.70   $36.70  
  Purchase #2 $103.73   9.858%   $113.9557   $113.96   $113.95   $114.00  
  Purchase #3 $125.42   5.272%   $132.0321   $132.03   $132.05   $132.00  
  Purchase #4 $129.61   10.597%   $143.3448   $143.34   $143.35   $143.30  
  Purchase #5 $203.58   11.181%   $226.3423   $226.34   $226.35   $226.30  
  Purchase #6 $170.52   9.530%   $186.7706   $186.77   $186.75   $186.80  
  Purchase #7 $173.67   11.164%   $193.0585   $193.06   $193.05   $193.10  
  7 purchase totals = $938.95       $1,032.2190   $1,032.22   $1,032.20   $1,032.20