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 $65.94   3.214%   $68.0593   $68.06   $68.05   $68.10  
  Purchase #2 $157.43   6.109%   $167.0474   $167.05   $167.05   $167.00  
  Purchase #3 $123.61   4.812%   $129.5581   $129.56   $129.55   $129.60  
  Purchase #4 $73.53   4.509%   $76.8455   $76.85   $76.85   $76.80  
  Purchase #5 $157.77   4.228%   $164.4405   $164.44   $164.45   $164.40  
  Purchase #6 $172.69   4.825%   $181.0223   $181.02   $181.00   $181.00  
  Purchase #7 $150.73   8.712%   $163.8616   $163.86   $163.85   $163.90  
  7 purchase totals = $901.70       $950.8347   $950.84   $950.80   $950.80