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 $216.41   4.808%   $226.815   $226.82   $226.80   $226.80  
  Purchase #2 $244.25   6.754%   $260.7466   $260.75   $260.75   $260.70  
  Purchase #3 $58.57   5.516%   $61.8007   $61.80   $61.80   $61.80  
  Purchase #4 $68.70   12.528%   $77.3067   $77.31   $77.30   $77.30  
  Purchase #5 $144.69   8.218%   $156.5806   $156.58   $156.60   $156.60  
  Purchase #6 $164.26   11.434%   $183.0415   $183.04   $183.05   $183.00  
  Purchase #7 $217.34   9.674%   $238.3655   $238.37   $238.35   $238.40  
  7 purchase totals = $1,114.22       $1,204.6566   $1,204.67   $1,204.65   $1,204.60