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 $174.65   11.599%   $194.9077   $194.91   $194.90   $194.90  
  Purchase #2 $200.98   8.147%   $217.3538   $217.35   $217.35   $217.40  
  Purchase #3 $43.71   7.285%   $46.8943   $46.89   $46.90   $46.90  
  Purchase #4 $163.70   8.862%   $178.2071   $178.21   $178.20   $178.20  
  Purchase #5 $10.58   9.595%   $11.5952   $11.60   $11.60   $11.60  
  Purchase #6 $191.91   6.109%   $203.6338   $203.63   $203.65   $203.60  
  Purchase #7 $212.91   5.232%   $224.0495   $224.05   $224.05   $224.00  
  7 purchase totals = $998.44       $1,076.6414   $1,076.64   $1,076.65   $1,076.60