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 $56.37   6.352%   $59.9506   $59.95   $59.95   $60.00  
  Purchase #2 $139.63   10.645%   $154.4936   $154.49   $154.50   $154.50  
  Purchase #3 $198.59   11.412%   $221.2531   $221.25   $221.25   $221.30  
  Purchase #4 $230.73   7.784%   $248.69   $248.69   $248.70   $248.70  
  Purchase #5 $249.80   7.494%   $268.52   $268.52   $268.50   $268.50  
  Purchase #6 $174.54   7.596%   $187.7981   $187.80   $187.80   $187.80  
  Purchase #7 $51.96   5.690%   $54.9165   $54.92   $54.90   $54.90  
  7 purchase totals = $1,101.62       $1,195.6219   $1,195.62   $1,195.60   $1,195.70