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 $192.77   6.764%   $205.809   $205.81   $205.80   $205.80  
  Purchase #2 $75.56   8.182%   $81.7423   $81.74   $81.75   $81.70  
  Purchase #3 $55.60   13.469%   $63.0888   $63.09   $63.10   $63.10  
  Purchase #4 $154.67   13.788%   $175.9959   $176.00   $176.00   $176.00  
  Purchase #5 $242.52   6.593%   $258.5093   $258.51   $258.50   $258.50  
  Purchase #6 $171.29   9.258%   $187.148   $187.15   $187.15   $187.10  
  Purchase #7 $135.67   9.171%   $148.1123   $148.11   $148.10   $148.10  
  7 purchase totals = $1,028.08       $1,120.4056   $1,120.41   $1,120.40   $1,120.30