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 $177.41   11.371%   $197.5833   $197.58   $197.60   $197.60  
  Purchase #2 $230.69   4.705%   $241.544   $241.54   $241.55   $241.50  
  Purchase #3 $98.33   10.592%   $108.7451   $108.75   $108.75   $108.70  
  Purchase #4 $114.65   6.224%   $121.7858   $121.79   $121.80   $121.80  
  Purchase #5 $153.49   4.392%   $160.2313   $160.23   $160.25   $160.20  
  Purchase #6 $21.72   11.499%   $24.2176   $24.22   $24.20   $24.20  
  Purchase #7 $173.66   5.797%   $183.7271   $183.73   $183.75   $183.70  
  7 purchase totals = $969.95       $1,037.8342   $1,037.84   $1,037.90   $1,037.70