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 $216.59   4.667%   $226.6983   $226.70   $226.70   $226.70  
  Purchase #2 $48.36   11.454%   $53.8992   $53.90   $53.90   $53.90  
  Purchase #3 $194.61   8.724%   $211.5878   $211.59   $211.60   $211.60  
  Purchase #4 $114.77   8.322%   $124.3212   $124.32   $124.30   $124.30  
  Purchase #5 $117.94   6.167%   $125.2134   $125.21   $125.20   $125.20  
  Purchase #6 $149.96   3.254%   $154.8397   $154.84   $154.85   $154.80  
  Purchase #7 $151.43   6.437%   $161.1775   $161.18   $161.20   $161.20  
  7 purchase totals = $993.66       $1,057.7371   $1,057.74   $1,057.75   $1,057.70