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 $196.90   7.652%   $211.9668   $211.97   $211.95   $212.00  
  Purchase #2 $86.77   7.220%   $93.0348   $93.03   $93.05   $93.00  
  Purchase #3 $140.80   7.490%   $151.3459   $151.35   $151.35   $151.30  
  Purchase #4 $155.27   13.122%   $175.6445   $175.64   $175.65   $175.60  
  Purchase #5 $187.26   13.410%   $212.3716   $212.37   $212.35   $212.40  
  Purchase #6 $162.27   8.716%   $176.4135   $176.41   $176.40   $176.40  
  Purchase #7 $5.92   3.161%   $6.1071   $6.11   $6.10   $6.10  
  7 purchase totals = $935.19       $1,026.8842   $1,026.88   $1,026.85   $1,026.80