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 $196.29   5.434%   $206.9564   $206.96   $206.95   $207.00  
  Purchase #2 $112.32   5.406%   $118.392   $118.39   $118.40   $118.40  
  Purchase #3 $213.29   11.801%   $238.4604   $238.46   $238.45   $238.50  
  Purchase #4 $24.56   4.444%   $25.6514   $25.65   $25.65   $25.70  
  Purchase #5 $69.37   9.489%   $75.9525   $75.95   $75.95   $76.00  
  Purchase #6 $45.36   5.724%   $47.9564   $47.96   $47.95   $48.00  
  Purchase #7 $238.30   6.239%   $253.1675   $253.17   $253.15   $253.20  
  7 purchase totals = $899.49       $966.5366   $966.54   $966.50   $966.80