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 $41.25   7.328%   $44.2728   $44.27   $44.25   $44.30  
  Purchase #2 $168.52   9.281%   $184.1603   $184.16   $184.15   $184.20  
  Purchase #3 $116.58   11.228%   $129.6696   $129.67   $129.65   $129.70  
  Purchase #4 $194.35   13.481%   $220.5503   $220.55   $220.55   $220.60  
  Purchase #5 $196.45   10.204%   $216.4958   $216.50   $216.50   $216.50  
  Purchase #6 $178.49   3.380%   $184.523   $184.52   $184.50   $184.50  
  Purchase #7 $122.77   11.271%   $136.6074   $136.61   $136.60   $136.60  
  7 purchase totals = $1,018.41       $1,116.2792   $1,116.28   $1,116.20   $1,116.40