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 $114.85   8.649%   $124.7834   $124.78   $124.80   $124.80  
  Purchase #2 $213.88   9.408%   $234.0018   $234.00   $234.00   $234.00  
  Purchase #3 $236.36   4.225%   $246.3462   $246.35   $246.35   $246.30  
  Purchase #4 $85.34   6.227%   $90.6541   $90.65   $90.65   $90.70  
  Purchase #5 $47.42   10.147%   $52.2317   $52.23   $52.25   $52.20  
  Purchase #6 $143.57   8.526%   $155.8108   $155.81   $155.80   $155.80  
  Purchase #7 $153.67   11.700%   $171.6494   $171.65   $171.65   $171.60  
  7 purchase totals = $995.09       $1,075.4774   $1,075.47   $1,075.50   $1,075.40