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 $58.85   5.524%   $62.1009   $62.10   $62.10   $62.10  
  Purchase #2 $149.57   8.124%   $161.7211   $161.72   $161.70   $161.70  
  Purchase #3 $229.64   3.563%   $237.8221   $237.82   $237.80   $237.80  
  Purchase #4 $86.33   8.365%   $93.5515   $93.55   $93.55   $93.60  
  Purchase #5 $87.40   6.134%   $92.7611   $92.76   $92.75   $92.80  
  Purchase #6 $171.35   9.756%   $188.0669   $188.07   $188.05   $188.10  
  Purchase #7 $149.99   4.255%   $156.3721   $156.37   $156.35   $156.40  
  7 purchase totals = $933.13       $992.3957   $992.39   $992.30   $992.50