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 $44.79   5.291%   $47.1598   $47.16   $47.15   $47.20  
  Purchase #2 $222.31   13.321%   $251.9239   $251.92   $251.90   $251.90  
  Purchase #3 $63.71   12.113%   $71.4272   $71.43   $71.45   $71.40  
  Purchase #4 $210.96   8.241%   $228.3452   $228.35   $228.35   $228.30  
  Purchase #5 $108.44   4.602%   $113.4304   $113.43   $113.45   $113.40  
  Purchase #6 $165.29   10.511%   $182.6636   $182.66   $182.65   $182.70  
  Purchase #7 $103.42   9.390%   $113.1311   $113.13   $113.15   $113.10  
  7 purchase totals = $918.92       $1,008.0812   $1,008.08   $1,008.10   $1,008.00