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 $194.65   3.846%   $202.1362   $202.14   $202.15   $202.10  
  Purchase #2 $86.44   11.260%   $96.1731   $96.17   $96.15   $96.20  
  Purchase #3 $235.33   3.831%   $244.3455   $244.35   $244.35   $244.30  
  Purchase #4 $38.89   12.400%   $43.7124   $43.71   $43.70   $43.70  
  Purchase #5 $239.76   10.198%   $264.2107   $264.21   $264.20   $264.20  
  Purchase #6 $227.60   10.529%   $251.564   $251.56   $251.55   $251.60  
  Purchase #7 $144.77   12.792%   $163.289   $163.29   $163.30   $163.30  
  7 purchase totals = $1,167.44       $1,265.4309   $1,265.43   $1,265.40   $1,265.40