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 $58.63   8.362%   $63.5326   $63.53   $63.55   $63.50  
  Purchase #2 $236.82   6.391%   $251.9552   $251.96   $251.95   $252.00  
  Purchase #3 $231.59   12.463%   $260.4531   $260.45   $260.45   $260.50  
  Purchase #4 $157.54   10.583%   $174.2125   $174.21   $174.20   $174.20  
  Purchase #5 $173.70   6.571%   $185.1138   $185.11   $185.10   $185.10  
  Purchase #6 $47.43   13.714%   $53.9346   $53.93   $53.95   $53.90  
  Purchase #7 $176.46   6.169%   $187.3458   $187.35   $187.35   $187.30  
  7 purchase totals = $1,082.17       $1,176.5476   $1,176.54   $1,176.55   $1,176.50