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 $195.26   3.274%   $201.6528   $201.65   $201.65   $201.70  
  Purchase #2 $238.39   12.852%   $269.0279   $269.03   $269.05   $269.00  
  Purchase #3 $32.87   11.114%   $36.5232   $36.52   $36.50   $36.50  
  Purchase #4 $105.78   5.183%   $111.2626   $111.26   $111.25   $111.30  
  Purchase #5 $234.72   5.746%   $248.207   $248.21   $248.20   $248.20  
  Purchase #6 $121.27   13.104%   $137.1612   $137.16   $137.15   $137.20  
  Purchase #7 $64.41   8.864%   $70.1193   $70.12   $70.10   $70.10  
  7 purchase totals = $992.70       $1,073.9540   $1,073.95   $1,073.90   $1,074.00