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 $114.54   10.415%   $126.4693   $126.47   $126.45   $126.50  
  Purchase #2 $75.34   7.262%   $80.8112   $80.81   $80.80   $80.80  
  Purchase #3 $65.63   13.755%   $74.6574   $74.66   $74.65   $74.70  
  Purchase #4 $244.46   7.177%   $262.0049   $262.00   $262.00   $262.00  
  Purchase #5 $151.69   11.485%   $169.1116   $169.11   $169.10   $169.10  
  Purchase #6 $168.28   9.865%   $184.8808   $184.88   $184.90   $184.90  
  Purchase #7 $121.86   11.201%   $135.5095   $135.51   $135.50   $135.50  
  7 purchase totals = $941.80       $1,033.4447   $1,033.44   $1,033.40   $1,033.50