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 $43.76   11.670%   $48.8668   $48.87   $48.85   $48.90  
  Purchase #2 $90.58   5.364%   $95.4387   $95.44   $95.45   $95.40  
  Purchase #3 $81.49   13.590%   $92.5645   $92.56   $92.55   $92.60  
  Purchase #4 $207.92   7.606%   $223.7344   $223.73   $223.75   $223.70  
  Purchase #5 $192.96   6.663%   $205.8169   $205.82   $205.80   $205.80  
  Purchase #6 $49.31   10.782%   $54.6266   $54.63   $54.65   $54.60  
  Purchase #7 $189.78   8.360%   $205.6456   $205.65   $205.65   $205.60  
  7 purchase totals = $855.80       $926.6935   $926.70   $926.70   $926.60