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 $219.76   5.697%   $232.2797   $232.28   $232.30   $232.30  
  Purchase #2 $248.26   9.807%   $272.6069   $272.61   $272.60   $272.60  
  Purchase #3 $152.79   10.383%   $168.6542   $168.65   $168.65   $168.70  
  Purchase #4 $47.83   10.291%   $52.7522   $52.75   $52.75   $52.80  
  Purchase #5 $117.51   13.823%   $133.7534   $133.75   $133.75   $133.80  
  Purchase #6 $151.30   5.816%   $160.0996   $160.10   $160.10   $160.10  
  Purchase #7 $24.55   7.352%   $26.3549   $26.35   $26.35   $26.40  
  7 purchase totals = $962.00       $1,046.5009   $1,046.49   $1,046.50   $1,046.70