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 $102.25   11.453%   $113.9607   $113.96   $113.95   $114.00  
  Purchase #2 $37.92   9.284%   $41.4405   $41.44   $41.45   $41.40  
  Purchase #3 $219.80   4.558%   $229.8185   $229.82   $229.80   $229.80  
  Purchase #4 $59.52   7.182%   $63.7947   $63.79   $63.80   $63.80  
  Purchase #5 $205.47   4.124%   $213.9436   $213.94   $213.95   $213.90  
  Purchase #6 $154.95   4.590%   $162.0622   $162.06   $162.05   $162.10  
  Purchase #7 $212.43   13.377%   $240.8468   $240.85   $240.85   $240.80  
  7 purchase totals = $992.34       $1,065.8670   $1,065.86   $1,065.85   $1,065.80