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 $194.74   5.780%   $205.996   $206.00   $206.00   $206.00  
  Purchase #2 $65.76   6.119%   $69.7839   $69.78   $69.80   $69.80  
  Purchase #3 $82.56   7.303%   $88.5894   $88.59   $88.60   $88.60  
  Purchase #4 $10.64   5.571%   $11.2328   $11.23   $11.25   $11.20  
  Purchase #5 $203.87   6.189%   $216.4875   $216.49   $216.50   $216.50  
  Purchase #6 $17.40   6.367%   $18.5079   $18.51   $18.50   $18.50  
  Purchase #7 $95.78   5.633%   $101.1753   $101.18   $101.20   $101.20  
  7 purchase totals = $670.75       $711.7728   $711.78   $711.85   $711.80