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 $68.42   11.441%   $76.2479   $76.25   $76.25   $76.20  
  Purchase #2 $193.30   8.465%   $209.6628   $209.66   $209.65   $209.70  
  Purchase #3 $189.55   13.338%   $214.8322   $214.83   $214.85   $214.80  
  Purchase #4 $179.44   10.212%   $197.7644   $197.76   $197.75   $197.80  
  Purchase #5 $198.83   7.633%   $214.0067   $214.01   $214.00   $214.00  
  Purchase #6 $64.70   6.455%   $68.8764   $68.88   $68.90   $68.90  
  Purchase #7 $77.95   11.782%   $87.1341   $87.13   $87.15   $87.10  
  7 purchase totals = $972.19       $1,068.5245   $1,068.52   $1,068.55   $1,068.50