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 $158.62   7.712%   $170.8528   $170.85   $170.85   $170.90  
  Purchase #2 $115.59   10.428%   $127.6437   $127.64   $127.65   $127.60  
  Purchase #3 $163.88   7.403%   $176.012   $176.01   $176.00   $176.00  
  Purchase #4 $198.35   6.677%   $211.5938   $211.59   $211.60   $211.60  
  Purchase #5 $208.82   5.811%   $220.9545   $220.95   $220.95   $221.00  
  Purchase #6 $101.43   3.260%   $104.7366   $104.74   $104.75   $104.70  
  Purchase #7 $148.59   5.440%   $156.6733   $156.67   $156.65   $156.70  
  7 purchase totals = $1,095.28       $1,168.4667   $1,168.45   $1,168.45   $1,168.50