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 $167.61   8.612%   $182.0446   $182.04   $182.05   $182.00  
  Purchase #2 $149.48   7.598%   $160.8375   $160.84   $160.85   $160.80  
  Purchase #3 $74.47   4.687%   $77.9604   $77.96   $77.95   $78.00  
  Purchase #4 $162.64   5.873%   $172.1918   $172.19   $172.20   $172.20  
  Purchase #5 $239.87   9.635%   $262.9815   $262.98   $263.00   $263.00  
  Purchase #6 $104.95   8.872%   $114.2612   $114.26   $114.25   $114.30  
  Purchase #7 $200.68   5.270%   $211.2558   $211.26   $211.25   $211.30  
  7 purchase totals = $1,099.70       $1,181.5328   $1,181.53   $1,181.55   $1,181.60