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 $164.49   6.797%   $175.6704   $175.67   $175.65   $175.70  
  Purchase #2 $28.85   9.295%   $31.5316   $31.53   $31.55   $31.50  
  Purchase #3 $99.65   7.355%   $106.9793   $106.98   $107.00   $107.00  
  Purchase #4 $125.53   6.694%   $133.933   $133.93   $133.95   $133.90  
  Purchase #5 $185.53   6.523%   $197.6321   $197.63   $197.65   $197.60  
  Purchase #6 $192.95   7.608%   $207.6296   $207.63   $207.65   $207.60  
  Purchase #7 $184.79   9.642%   $202.6075   $202.61   $202.60   $202.60  
  7 purchase totals = $981.79       $1,055.9835   $1,055.98   $1,056.05   $1,055.90