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 $181.33   10.854%   $201.0116   $201.01   $201.00   $201.00  
  Purchase #2 $217.53   5.347%   $229.1613   $229.16   $229.15   $229.20  
  Purchase #3 $243.33   11.533%   $271.3932   $271.39   $271.40   $271.40  
  Purchase #4 $151.74   10.432%   $167.5695   $167.57   $167.55   $167.60  
  Purchase #5 $190.50   10.833%   $211.1369   $211.14   $211.15   $211.10  
  Purchase #6 $173.57   6.354%   $184.5986   $184.60   $184.60   $184.60  
  Purchase #7 $79.99   3.104%   $82.4729   $82.47   $82.45   $82.50  
  7 purchase totals = $1,237.99       $1,347.3440   $1,347.34   $1,347.30   $1,347.40