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 $61.85   9.345%   $67.6299   $67.63   $67.65   $67.60  
  Purchase #2 $104.82   8.223%   $113.4393   $113.44   $113.45   $113.40  
  Purchase #3 $168.85   11.807%   $188.7861   $188.79   $188.80   $188.80  
  Purchase #4 $92.85   6.736%   $99.1044   $99.10   $99.10   $99.10  
  Purchase #5 $64.44   6.603%   $68.695   $68.70   $68.70   $68.70  
  Purchase #6 $231.62   11.135%   $257.4109   $257.41   $257.40   $257.40  
  Purchase #7 $10.53   10.872%   $11.6748   $11.67   $11.65   $11.70  
  7 purchase totals = $734.96       $806.7404   $806.74   $806.75   $806.70