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 $214.89   13.537%   $243.9797   $243.98   $244.00   $244.00  
  Purchase #2 $238.97   9.199%   $260.9529   $260.95   $260.95   $261.00  
  Purchase #3 $176.97   6.807%   $189.0163   $189.02   $189.00   $189.00  
  Purchase #4 $119.35   12.712%   $134.5218   $134.52   $134.50   $134.50  
  Purchase #5 $127.57   11.394%   $142.1053   $142.11   $142.10   $142.10  
  Purchase #6 $214.62   3.530%   $222.1961   $222.20   $222.20   $222.20  
  Purchase #7 $63.72   13.744%   $72.4777   $72.48   $72.50   $72.50  
  7 purchase totals = $1,156.09       $1,265.2498   $1,265.26   $1,265.25   $1,265.30