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 $43.68   9.192%   $47.6951   $47.70   $47.70   $47.70  
  Purchase #2 $106.75   6.562%   $113.7549   $113.75   $113.75   $113.80  
  Purchase #3 $55.77   13.639%   $63.3765   $63.38   $63.40   $63.40  
  Purchase #4 $237.71   4.324%   $247.9886   $247.99   $248.00   $248.00  
  Purchase #5 $182.37   5.731%   $192.8216   $192.82   $192.80   $192.80  
  Purchase #6 $174.46   11.716%   $194.8997   $194.90   $194.90   $194.90  
  Purchase #7 $181.78   11.825%   $203.2755   $203.28   $203.30   $203.30  
  7 purchase totals = $982.52       $1,063.8119   $1,063.82   $1,063.85   $1,063.90