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 $246.83   9.185%   $269.5013   $269.50   $269.50   $269.50  
  Purchase #2 $67.39   9.470%   $73.7718   $73.77   $73.75   $73.80  
  Purchase #3 $73.57   10.471%   $81.2735   $81.27   $81.25   $81.30  
  Purchase #4 $55.45   11.394%   $61.768   $61.77   $61.75   $61.80  
  Purchase #5 $129.30   13.429%   $146.6637   $146.66   $146.65   $146.70  
  Purchase #6 $225.94   3.405%   $233.6333   $233.63   $233.65   $233.60  
  Purchase #7 $169.64   10.647%   $187.7016   $187.70   $187.70   $187.70  
  7 purchase totals = $968.12       $1,054.3132   $1,054.30   $1,054.25   $1,054.40