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 $72.65   6.425%   $77.3178   $77.32   $77.30   $77.30  
  Purchase #2 $192.64   5.873%   $203.9537   $203.95   $203.95   $204.00  
  Purchase #3 $180.46   8.609%   $195.9958   $196.00   $196.00   $196.00  
  Purchase #4 $226.37   7.345%   $242.9969   $243.00   $243.00   $243.00  
  Purchase #5 $69.77   12.564%   $78.5359   $78.54   $78.55   $78.50  
  Purchase #6 $187.89   11.425%   $209.3564   $209.36   $209.35   $209.40  
  Purchase #7 $104.26   5.375%   $109.864   $109.86   $109.85   $109.90  
  7 purchase totals = $1,034.04       $1,118.0205   $1,118.03   $1,118.00   $1,118.10