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 $136.61   12.242%   $153.3338   $153.33   $153.35   $153.30  
  Purchase #2 $202.74   7.627%   $218.203   $218.20   $218.20   $218.20  
  Purchase #3 $185.34   8.699%   $201.4627   $201.46   $201.45   $201.50  
  Purchase #4 $67.86   5.346%   $71.4878   $71.49   $71.50   $71.50  
  Purchase #5 $182.86   7.575%   $196.7116   $196.71   $196.70   $196.70  
  Purchase #6 $197.36   7.302%   $211.7712   $211.77   $211.75   $211.80  
  Purchase #7 $96.65   11.433%   $107.7   $107.70   $107.70   $107.70  
  7 purchase totals = $1,069.42       $1,160.6701   $1,160.66   $1,160.65   $1,160.70