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 $186.26   10.412%   $205.6534   $205.65   $205.65   $205.70  
  Purchase #2 $67.33   8.381%   $72.9729   $72.97   $72.95   $73.00  
  Purchase #3 $36.30   3.106%   $37.4275   $37.43   $37.45   $37.40  
  Purchase #4 $186.91   13.760%   $212.6288   $212.63   $212.65   $212.60  
  Purchase #5 $150.70   5.387%   $158.8182   $158.82   $158.80   $158.80  
  Purchase #6 $220.70   5.488%   $232.812   $232.81   $232.80   $232.80  
  Purchase #7 $173.65   6.201%   $184.418   $184.42   $184.40   $184.40  
  7 purchase totals = $1,021.85       $1,104.7308   $1,104.73   $1,104.70   $1,104.70