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 $181.89   10.471%   $200.9357   $200.94   $200.95   $200.90  
  Purchase #2 $76.88   5.501%   $81.1092   $81.11   $81.10   $81.10  
  Purchase #3 $164.66   11.724%   $183.9647   $183.96   $183.95   $184.00  
  Purchase #4 $229.99   6.519%   $244.983   $244.98   $245.00   $245.00  
  Purchase #5 $72.62   6.828%   $77.5785   $77.58   $77.60   $77.60  
  Purchase #6 $248.55   7.759%   $267.835   $267.84   $267.85   $267.80  
  Purchase #7 $108.35   7.609%   $116.5944   $116.59   $116.60   $116.60  
  7 purchase totals = $1,082.94       $1,173.0005   $1,173.00   $1,173.05   $1,173.00