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 $202.87   5.524%   $214.0765   $214.08   $214.10   $214.10  
  Purchase #2 $50.59   6.613%   $53.9355   $53.94   $53.95   $53.90  
  Purchase #3 $180.60   5.752%   $190.9881   $190.99   $191.00   $191.00  
  Purchase #4 $211.28   4.581%   $220.9587   $220.96   $220.95   $221.00  
  Purchase #5 $179.41   6.305%   $190.7218   $190.72   $190.70   $190.70  
  Purchase #6 $53.81   13.319%   $60.977   $60.98   $61.00   $61.00  
  Purchase #7 $167.97   6.771%   $179.3432   $179.34   $179.35   $179.30  
  7 purchase totals = $1,046.53       $1,111.0008   $1,111.01   $1,111.05   $1,111.00