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 $209.78   7.595%   $225.7128   $225.71   $225.70   $225.70  
  Purchase #2 $242.93   4.205%   $253.1452   $253.15   $253.15   $253.10  
  Purchase #3 $8.96   4.444%   $9.3582   $9.36   $9.35   $9.40  
  Purchase #4 $225.34   5.699%   $238.1821   $238.18   $238.20   $238.20  
  Purchase #5 $25.35   6.557%   $27.0122   $27.01   $27.00   $27.00  
  Purchase #6 $99.67   4.811%   $104.4651   $104.47   $104.45   $104.50  
  Purchase #7 $221.78   11.171%   $246.555   $246.56   $246.55   $246.60  
  7 purchase totals = $1,033.81       $1,104.4306   $1,104.44   $1,104.40   $1,104.50