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 $44.64   5.267%   $46.9912   $46.99   $47.00   $47.00  
  Purchase #2 $137.78   11.410%   $153.5007   $153.50   $153.50   $153.50  
  Purchase #3 $197.39   10.369%   $217.8574   $217.86   $217.85   $217.90  
  Purchase #4 $218.37   9.782%   $239.731   $239.73   $239.75   $239.70  
  Purchase #5 $192.70   10.648%   $213.2187   $213.22   $213.20   $213.20  
  Purchase #6 $114.36   8.243%   $123.7867   $123.79   $123.80   $123.80  
  Purchase #7 $42.65   4.170%   $44.4285   $44.43   $44.45   $44.40  
  7 purchase totals = $947.89       $1,039.5142   $1,039.52   $1,039.55   $1,039.50