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 $72.63   6.160%   $77.104   $77.10   $77.10   $77.10  
  Purchase #2 $189.56   9.272%   $207.136   $207.14   $207.15   $207.10  
  Purchase #3 $239.67   8.204%   $259.3325   $259.33   $259.35   $259.30  
  Purchase #4 $60.86   3.452%   $62.9609   $62.96   $62.95   $63.00  
  Purchase #5 $115.82   5.137%   $121.7697   $121.77   $121.75   $121.80  
  Purchase #6 $168.71   13.170%   $190.9291   $190.93   $190.95   $190.90  
  Purchase #7 $120.58   11.737%   $134.7325   $134.73   $134.75   $134.70  
  7 purchase totals = $967.83       $1,053.9647   $1,053.96   $1,054.00   $1,053.90