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 $182.76   9.202%   $199.5776   $199.58   $199.60   $199.60  
  Purchase #2 $119.59   5.824%   $126.5549   $126.55   $126.55   $126.60  
  Purchase #3 $174.55   9.375%   $190.9141   $190.91   $190.90   $190.90  
  Purchase #4 $36.43   8.213%   $39.422   $39.42   $39.40   $39.40  
  Purchase #5 $201.59   12.772%   $227.3371   $227.34   $227.35   $227.30  
  Purchase #6 $106.28   12.229%   $119.277   $119.28   $119.30   $119.30  
  Purchase #7 $181.33   6.197%   $192.567   $192.57   $192.55   $192.60  
  7 purchase totals = $1,002.53       $1,095.6497   $1,095.65   $1,095.65   $1,095.70