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 $195.78   3.113%   $201.8746   $201.87   $201.85   $201.90  
  Purchase #2 $234.34   13.490%   $265.9525   $265.95   $265.95   $266.00  
  Purchase #3 $32.59   9.315%   $35.6258   $35.63   $35.65   $35.60  
  Purchase #4 $86.36   4.815%   $90.5182   $90.52   $90.50   $90.50  
  Purchase #5 $8.77   12.244%   $9.8438   $9.84   $9.85   $9.80  
  Purchase #6 $245.48   9.328%   $268.3784   $268.38   $268.40   $268.40  
  Purchase #7 $71.43   3.825%   $74.1622   $74.16   $74.15   $74.20  
  7 purchase totals = $874.75       $946.3555   $946.35   $946.35   $946.40