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 $33.65   4.743%   $35.246   $35.25   $35.25   $35.20  
  Purchase #2 $184.94   5.619%   $195.3318   $195.33   $195.35   $195.30  
  Purchase #3 $85.99   8.430%   $93.239   $93.24   $93.25   $93.20  
  Purchase #4 $243.95   13.699%   $277.3687   $277.37   $277.35   $277.40  
  Purchase #5 $44.72   5.298%   $47.0893   $47.09   $47.10   $47.10  
  Purchase #6 $165.29   13.405%   $187.4471   $187.45   $187.45   $187.40  
  Purchase #7 $233.59   12.419%   $262.5995   $262.60   $262.60   $262.60  
  7 purchase totals = $992.13       $1,098.3214   $1,098.33   $1,098.35   $1,098.20