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   5.746%   $173.9416   $173.94   $173.95   $173.90  
  Purchase #2 $187.34   9.174%   $204.5266   $204.53   $204.55   $204.50  
  Purchase #3 $181.99   4.288%   $189.7937   $189.79   $189.80   $189.80  
  Purchase #4 $240.38   6.831%   $256.8004   $256.80   $256.80   $256.80  
  Purchase #5 $247.63   6.855%   $264.605   $264.61   $264.60   $264.60  
  Purchase #6 $175.93   13.234%   $199.2126   $199.21   $199.20   $199.20  
  Purchase #7 $140.43   4.328%   $146.5078   $146.51   $146.50   $146.50  
  7 purchase totals = $1,338.19       $1,435.3877   $1,435.39   $1,435.40   $1,435.30