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 $86.45   8.772%   $94.0334   $94.03   $94.05   $94.00  
  Purchase #2 $154.49   4.344%   $161.201   $161.20   $161.20   $161.20  
  Purchase #3 $97.85   9.380%   $107.0283   $107.03   $107.05   $107.00  
  Purchase #4 $52.32   11.159%   $58.1584   $58.16   $58.15   $58.20  
  Purchase #5 $250.97   8.391%   $272.0289   $272.03   $272.05   $272.00  
  Purchase #6 $179.59   13.650%   $204.104   $204.10   $204.10   $204.10  
  Purchase #7 $110.88   6.439%   $118.0196   $118.02   $118.00   $118.00  
  7 purchase totals = $932.55       $1,014.5736   $1,014.57   $1,014.60   $1,014.50