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 $64.90   12.701%   $73.1429   $73.14   $73.15   $73.10  
  Purchase #2 $243.52   4.532%   $254.5563   $254.56   $254.55   $254.60  
  Purchase #3 $196.70   7.325%   $211.1083   $211.11   $211.10   $211.10  
  Purchase #4 $156.51   5.782%   $165.5594   $165.56   $165.55   $165.60  
  Purchase #5 $192.75   3.724%   $199.928   $199.93   $199.95   $199.90  
  Purchase #6 $45.27   3.138%   $46.6906   $46.69   $46.70   $46.70  
  Purchase #7 $208.94   7.691%   $225.0096   $225.01   $225.00   $225.00  
  7 purchase totals = $1,108.59       $1,175.9951   $1,176.00   $1,176.00   $1,176.00