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 $84.28   13.851%   $95.9536   $95.95   $95.95   $96.00  
  Purchase #2 $230.42   11.827%   $257.6718   $257.67   $257.65   $257.70  
  Purchase #3 $109.54   10.744%   $121.309   $121.31   $121.30   $121.30  
  Purchase #4 $99.31   10.398%   $109.6363   $109.64   $109.65   $109.60  
  Purchase #5 $46.32   3.194%   $47.7995   $47.80   $47.80   $47.80  
  Purchase #6 $246.35   3.366%   $254.6421   $254.64   $254.65   $254.60  
  Purchase #7 $187.48   13.211%   $212.248   $212.25   $212.25   $212.20  
  7 purchase totals = $1,003.70       $1,099.2603   $1,099.26   $1,099.25   $1,099.20