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 $237.56   6.340%   $252.6213   $252.62   $252.60   $252.60  
  Purchase #2 $130.99   3.440%   $135.4961   $135.50   $135.50   $135.50  
  Purchase #3 $47.64   3.784%   $49.4427   $49.44   $49.45   $49.40  
  Purchase #4 $249.86   9.645%   $273.959   $273.96   $273.95   $274.00  
  Purchase #5 $88.73   7.134%   $95.06   $95.06   $95.05   $95.10  
  Purchase #6 $86.68   5.777%   $91.6875   $91.69   $91.70   $91.70  
  Purchase #7 $110.69   5.145%   $116.385   $116.39   $116.40   $116.40  
  7 purchase totals = $952.15       $1,014.6516   $1,014.66   $1,014.65   $1,014.70