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 $116.56   7.559%   $125.3708   $125.37   $125.35   $125.40  
  Purchase #2 $117.84   3.829%   $122.3521   $122.35   $122.35   $122.40  
  Purchase #3 $181.90   7.231%   $195.0532   $195.05   $195.05   $195.10  
  Purchase #4 $146.62   11.742%   $163.8361   $163.84   $163.85   $163.80  
  Purchase #5 $99.93   3.625%   $103.5525   $103.55   $103.55   $103.60  
  Purchase #6 $219.54   7.683%   $236.4073   $236.41   $236.40   $236.40  
  Purchase #7 $102.36   11.636%   $114.2706   $114.27   $114.25   $114.30  
  7 purchase totals = $984.75       $1,060.8426   $1,060.84   $1,060.80   $1,061.00