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 $43.48   7.155%   $46.591   $46.59   $46.60   $46.60  
  Purchase #2 $62.47   8.853%   $68.0005   $68.00   $68.00   $68.00  
  Purchase #3 $173.78   7.206%   $186.3026   $186.30   $186.30   $186.30  
  Purchase #4 $70.82   8.518%   $76.8524   $76.85   $76.85   $76.90  
  Purchase #5 $242.79   8.423%   $263.2402   $263.24   $263.25   $263.20  
  Purchase #6 $191.96   3.439%   $198.5615   $198.56   $198.55   $198.60  
  Purchase #7 $76.72   13.720%   $87.246   $87.25   $87.25   $87.20  
  7 purchase totals = $862.02       $926.7942   $926.79   $926.80   $926.80