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 $194.39   6.380%   $206.7921   $206.79   $206.80   $206.80  
  Purchase #2 $16.84   3.322%   $17.3994   $17.40   $17.40   $17.40  
  Purchase #3 $68.48   6.644%   $73.0298   $73.03   $73.05   $73.00  
  Purchase #4 $127.54   10.379%   $140.7774   $140.78   $140.80   $140.80  
  Purchase #5 $158.88   6.548%   $169.2835   $169.28   $169.30   $169.30  
  Purchase #6 $234.71   5.598%   $247.8491   $247.85   $247.85   $247.80  
  Purchase #7 $180.58   13.757%   $205.4224   $205.42   $205.40   $205.40  
  7 purchase totals = $981.42       $1,060.5537   $1,060.55   $1,060.60   $1,060.50