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 $106.60   5.651%   $112.624   $112.62   $112.60   $112.60  
  Purchase #2 $208.81   8.729%   $227.037   $227.04   $227.05   $227.00  
  Purchase #3 $220.71   8.730%   $239.978   $239.98   $240.00   $240.00  
  Purchase #4 $118.64   4.815%   $124.3525   $124.35   $124.35   $124.40  
  Purchase #5 $141.38   5.582%   $149.2718   $149.27   $149.25   $149.30  
  Purchase #6 $52.58   8.338%   $56.9641   $56.96   $56.95   $57.00  
  Purchase #7 $95.25   5.435%   $100.4268   $100.43   $100.45   $100.40  
  7 purchase totals = $943.97       $1,010.6542   $1,010.65   $1,010.65   $1,010.70