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 $55.41   8.283%   $59.9996   $60.00   $60.00   $60.00  
  Purchase #2 $187.45   12.794%   $211.4324   $211.43   $211.45   $211.40  
  Purchase #3 $117.46   8.481%   $127.4218   $127.42   $127.40   $127.40  
  Purchase #4 $107.69   9.677%   $118.1112   $118.11   $118.10   $118.10  
  Purchase #5 $219.26   9.771%   $240.6839   $240.68   $240.70   $240.70  
  Purchase #6 $150.92   4.841%   $158.226   $158.23   $158.25   $158.20  
  Purchase #7 $226.43   3.303%   $233.909   $233.91   $233.90   $233.90  
  7 purchase totals = $1,064.62       $1,149.7839   $1,149.78   $1,149.80   $1,149.70