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 $65.38   11.818%   $73.1066   $73.11   $73.10   $73.10  
  Purchase #2 $166.38   5.728%   $175.9102   $175.91   $175.90   $175.90  
  Purchase #3 $177.82   3.433%   $183.9246   $183.92   $183.90   $183.90  
  Purchase #4 $222.57   13.780%   $253.2401   $253.24   $253.25   $253.20  
  Purchase #5 $61.84   10.123%   $68.1001   $68.10   $68.10   $68.10  
  Purchase #6 $210.60   3.113%   $217.156   $217.16   $217.15   $217.20  
  Purchase #7 $140.26   8.545%   $152.2452   $152.25   $152.25   $152.20  
  7 purchase totals = $1,044.85       $1,123.6828   $1,123.69   $1,123.65   $1,123.60