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 $44.46   4.652%   $46.5283   $46.53   $46.55   $46.50  
  Purchase #2 $82.27   7.642%   $88.5571   $88.56   $88.55   $88.60  
  Purchase #3 $58.89   6.651%   $62.8068   $62.81   $62.80   $62.80  
  Purchase #4 $215.81   13.185%   $244.2645   $244.26   $244.25   $244.30  
  Purchase #5 $241.37   11.508%   $269.1469   $269.15   $269.15   $269.10  
  Purchase #6 $227.26   7.526%   $244.3636   $244.36   $244.35   $244.40  
  Purchase #7 $111.79   6.178%   $118.6964   $118.70   $118.70   $118.70  
  7 purchase totals = $981.85       $1,074.3636   $1,074.37   $1,074.35   $1,074.40