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 $87.96   8.669%   $95.5853   $95.59   $95.60   $95.60  
  Purchase #2 $91.87   10.714%   $101.713   $101.71   $101.70   $101.70  
  Purchase #3 $147.88   8.636%   $160.6509   $160.65   $160.65   $160.70  
  Purchase #4 $187.51   10.688%   $207.5511   $207.55   $207.55   $207.60  
  Purchase #5 $226.93   9.270%   $247.9664   $247.97   $247.95   $248.00  
  Purchase #6 $168.30   4.206%   $175.3787   $175.38   $175.40   $175.40  
  Purchase #7 $159.85   7.412%   $171.6981   $171.70   $171.70   $171.70  
  7 purchase totals = $1,070.30       $1,160.5435   $1,160.55   $1,160.55   $1,160.70