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 $71.65   5.462%   $75.5635   $75.56   $75.55   $75.60  
  Purchase #2 $152.57   3.302%   $157.6079   $157.61   $157.60   $157.60  
  Purchase #3 $198.58   9.790%   $218.021   $218.02   $218.00   $218.00  
  Purchase #4 $162.69   9.129%   $177.542   $177.54   $177.55   $177.50  
  Purchase #5 $188.79   11.337%   $210.1931   $210.19   $210.20   $210.20  
  Purchase #6 $236.92   4.488%   $247.553   $247.55   $247.55   $247.60  
  Purchase #7 $175.84   4.219%   $183.2587   $183.26   $183.25   $183.30  
  7 purchase totals = $1,187.04       $1,269.7392   $1,269.73   $1,269.70   $1,269.80