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 $91.64   4.609%   $95.8637   $95.86   $95.85   $95.90  
  Purchase #2 $167.93   5.715%   $177.5272   $177.53   $177.55   $177.50  
  Purchase #3 $218.64   12.561%   $246.1034   $246.10   $246.10   $246.10  
  Purchase #4 $198.79   13.112%   $224.8553   $224.86   $224.85   $224.90  
  Purchase #5 $216.77   7.812%   $233.7041   $233.70   $233.70   $233.70  
  Purchase #6 $123.71   5.619%   $130.6613   $130.66   $130.65   $130.70  
  Purchase #7 $77.58   12.272%   $87.1006   $87.10   $87.10   $87.10  
  7 purchase totals = $1,095.06       $1,195.8156   $1,195.81   $1,195.80   $1,195.90