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 $68.63   7.575%   $73.8287   $73.83   $73.85   $73.80  
  Purchase #2 $68.59   11.458%   $76.449   $76.45   $76.45   $76.40  
  Purchase #3 $193.47   6.302%   $205.6625   $205.66   $205.65   $205.70  
  Purchase #4 $202.80   4.417%   $211.7577   $211.76   $211.75   $211.80  
  Purchase #5 $151.64   4.362%   $158.2545   $158.25   $158.25   $158.30  
  Purchase #6 $129.87   3.161%   $133.9752   $133.98   $134.00   $134.00  
  Purchase #7 $148.64   7.349%   $159.5636   $159.56   $159.55   $159.60  
  7 purchase totals = $963.64       $1,019.4912   $1,019.49   $1,019.50   $1,019.60