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 $216.67   11.258%   $241.0627   $241.06   $241.05   $241.10  
  Purchase #2 $29.32   4.393%   $30.608   $30.61   $30.60   $30.60  
  Purchase #3 $190.43   3.800%   $197.6663   $197.67   $197.65   $197.70  
  Purchase #4 $243.54   9.658%   $267.0611   $267.06   $267.05   $267.10  
  Purchase #5 $80.83   13.154%   $91.4624   $91.46   $91.45   $91.50  
  Purchase #6 $84.45   10.164%   $93.0335   $93.03   $93.05   $93.00  
  Purchase #7 $198.45   7.147%   $212.6332   $212.63   $212.65   $212.60  
  7 purchase totals = $1,043.69       $1,133.5272   $1,133.52   $1,133.50   $1,133.60