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 $91.40   4.604%   $95.6081   $95.61   $95.60   $95.60  
  Purchase #2 $96.82   6.667%   $103.275   $103.28   $103.30   $103.30  
  Purchase #3 $170.44   13.213%   $192.9602   $192.96   $192.95   $193.00  
  Purchase #4 $236.34   4.335%   $246.5853   $246.59   $246.60   $246.60  
  Purchase #5 $92.62   4.342%   $96.6416   $96.64   $96.65   $96.60  
  Purchase #6 $248.66   7.549%   $267.4313   $267.43   $267.45   $267.40  
  Purchase #7 $208.94   5.580%   $220.5989   $220.60   $220.60   $220.60  
  7 purchase totals = $1,145.22       $1,223.1004   $1,223.11   $1,223.15   $1,223.10