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 $196.29   7.554%   $211.1177   $211.12   $211.10   $211.10  
  Purchase #2 $53.47   13.247%   $60.5532   $60.55   $60.55   $60.60  
  Purchase #3 $44.92   8.138%   $48.5756   $48.58   $48.60   $48.60  
  Purchase #4 $228.30   8.827%   $248.452   $248.45   $248.45   $248.50  
  Purchase #5 $31.90   4.365%   $33.2924   $33.29   $33.30   $33.30  
  Purchase #6 $220.78   10.453%   $243.8581   $243.86   $243.85   $243.90  
  Purchase #7 $163.48   8.170%   $176.8363   $176.84   $176.85   $176.80  
  7 purchase totals = $939.14       $1,022.6853   $1,022.69   $1,022.70   $1,022.80