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 $214.58   5.243%   $225.8304   $225.83   $225.85   $225.80  
  Purchase #2 $156.95   13.251%   $177.7474   $177.75   $177.75   $177.70  
  Purchase #3 $14.47   13.556%   $16.4316   $16.43   $16.45   $16.40  
  Purchase #4 $238.86   5.179%   $251.2306   $251.23   $251.25   $251.20  
  Purchase #5 $34.49   3.309%   $35.6313   $35.63   $35.65   $35.60  
  Purchase #6 $137.35   4.603%   $143.6722   $143.67   $143.65   $143.70  
  Purchase #7 $181.81   11.566%   $202.8381   $202.84   $202.85   $202.80  
  7 purchase totals = $978.51       $1,053.3816   $1,053.38   $1,053.45   $1,053.20