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 $184.75   9.849%   $202.946   $202.95   $202.95   $202.90  
  Purchase #2 $230.84   7.597%   $248.3769   $248.38   $248.40   $248.40  
  Purchase #3 $120.91   12.212%   $135.6755   $135.68   $135.70   $135.70  
  Purchase #4 $187.86   12.669%   $211.66   $211.66   $211.65   $211.70  
  Purchase #5 $177.61   10.734%   $196.6747   $196.67   $196.65   $196.70  
  Purchase #6 $189.55   11.322%   $211.0109   $211.01   $211.00   $211.00  
  Purchase #7 $235.52   4.416%   $245.9206   $245.92   $245.90   $245.90  
  7 purchase totals = $1,327.04       $1,452.2646   $1,452.27   $1,452.25   $1,452.30