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 $215.69   13.605%   $245.0346   $245.03   $245.05   $245.00  
  Purchase #2 $137.29   5.477%   $144.8094   $144.81   $144.80   $144.80  
  Purchase #3 $33.79   12.352%   $37.9637   $37.96   $37.95   $38.00  
  Purchase #4 $184.61   5.294%   $194.3833   $194.38   $194.40   $194.40  
  Purchase #5 $205.57   10.163%   $226.4621   $226.46   $226.45   $226.50  
  Purchase #6 $41.53   6.362%   $44.1721   $44.17   $44.15   $44.20  
  Purchase #7 $176.96   13.367%   $200.6142   $200.61   $200.60   $200.60  
  7 purchase totals = $995.44       $1,093.4394   $1,093.42   $1,093.40   $1,093.50