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 $95.42   11.848%   $106.7254   $106.73   $106.75   $106.70  
  Purchase #2 $202.77   11.753%   $226.6016   $226.60   $226.60   $226.60  
  Purchase #3 $55.66   13.636%   $63.2498   $63.25   $63.25   $63.20  
  Purchase #4 $16.63   6.771%   $17.756   $17.76   $17.75   $17.80  
  Purchase #5 $97.33   6.637%   $103.7898   $103.79   $103.80   $103.80  
  Purchase #6 $199.92   8.600%   $217.1131   $217.11   $217.10   $217.10  
  Purchase #7 $24.62   9.555%   $26.9724   $26.97   $26.95   $27.00  
  7 purchase totals = $692.35       $762.2081   $762.21   $762.20   $762.20