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 $212.77   5.764%   $225.0341   $225.03   $225.05   $225.00  
  Purchase #2 $61.52   8.278%   $66.6126   $66.61   $66.60   $66.60  
  Purchase #3 $185.58   3.650%   $192.3537   $192.35   $192.35   $192.40  
  Purchase #4 $183.58   13.411%   $208.1999   $208.20   $208.20   $208.20  
  Purchase #5 $161.62   5.281%   $170.1552   $170.16   $170.15   $170.20  
  Purchase #6 $189.25   13.132%   $214.1023   $214.10   $214.10   $214.10  
  Purchase #7 $222.45   10.773%   $246.4145   $246.41   $246.40   $246.40  
  7 purchase totals = $1,216.77       $1,322.8723   $1,322.86   $1,322.85   $1,322.90