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 $88.68   9.769%   $97.3431   $97.34   $97.35   $97.30  
  Purchase #2 $193.29   6.723%   $206.2849   $206.28   $206.30   $206.30  
  Purchase #3 $84.54   3.383%   $87.4   $87.40   $87.40   $87.40  
  Purchase #4 $246.58   5.721%   $260.6868   $260.69   $260.70   $260.70  
  Purchase #5 $199.30   3.718%   $206.71   $206.71   $206.70   $206.70  
  Purchase #6 $29.97   13.152%   $33.9117   $33.91   $33.90   $33.90  
  Purchase #7 $195.93   13.161%   $221.7163   $221.72   $221.70   $221.70  
  7 purchase totals = $1,038.29       $1,114.0528   $1,114.05   $1,114.05   $1,114.00