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 $67.81   10.157%   $74.6975   $74.70   $74.70   $74.70  
  Purchase #2 $228.91   6.724%   $244.3019   $244.30   $244.30   $244.30  
  Purchase #3 $88.40   4.358%   $92.2525   $92.25   $92.25   $92.30  
  Purchase #4 $197.47   6.847%   $210.9908   $210.99   $211.00   $211.00  
  Purchase #5 $116.89   5.828%   $123.7023   $123.70   $123.70   $123.70  
  Purchase #6 $239.50   10.489%   $264.6212   $264.62   $264.60   $264.60  
  Purchase #7 $210.28   5.421%   $221.6793   $221.68   $221.70   $221.70  
  7 purchase totals = $1,149.26       $1,232.2455   $1,232.24   $1,232.25   $1,232.30