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 $164.88   8.122%   $178.2716   $178.27   $178.25   $178.30  
  Purchase #2 $148.37   10.395%   $163.7931   $163.79   $163.80   $163.80  
  Purchase #3 $103.96   9.285%   $113.6127   $113.61   $113.60   $113.60  
  Purchase #4 $248.55   13.697%   $282.5939   $282.59   $282.60   $282.60  
  Purchase #5 $155.51   7.743%   $167.5511   $167.55   $167.55   $167.60  
  Purchase #6 $117.94   12.471%   $132.6483   $132.65   $132.65   $132.60  
  Purchase #7 $25.36   12.843%   $28.617   $28.62   $28.60   $28.60  
  7 purchase totals = $964.57       $1,067.0877   $1,067.08   $1,067.05   $1,067.10