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 $60.89   10.347%   $67.1903   $67.19   $67.20   $67.20  
  Purchase #2 $105.59   13.394%   $119.7327   $119.73   $119.75   $119.70  
  Purchase #3 $75.82   13.411%   $85.9882   $85.99   $86.00   $86.00  
  Purchase #4 $47.71   10.236%   $52.5936   $52.59   $52.60   $52.60  
  Purchase #5 $33.65   4.446%   $35.1461   $35.15   $35.15   $35.10  
  Purchase #6 $181.91   6.638%   $193.9852   $193.99   $194.00   $194.00  
  Purchase #7 $202.82   4.748%   $212.4499   $212.45   $212.45   $212.40  
  7 purchase totals = $708.39       $767.0860   $767.09   $767.15   $767.00