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 $92.29   3.756%   $95.7564   $95.76   $95.75   $95.80  
  Purchase #2 $170.97   7.416%   $183.6491   $183.65   $183.65   $183.60  
  Purchase #3 $10.97   10.429%   $12.1141   $12.11   $12.10   $12.10  
  Purchase #4 $186.89   7.232%   $200.4059   $200.41   $200.40   $200.40  
  Purchase #5 $48.68   12.348%   $54.691   $54.69   $54.70   $54.70  
  Purchase #6 $204.45   5.244%   $215.1714   $215.17   $215.15   $215.20  
  Purchase #7 $239.37   5.721%   $253.0644   $253.06   $253.05   $253.10  
  7 purchase totals = $953.62       $1,014.8523   $1,014.85   $1,014.80   $1,014.90