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 $160.96   7.273%   $172.6666   $172.67   $172.65   $172.70  
  Purchase #2 $212.57   11.373%   $236.7456   $236.75   $236.75   $236.70  
  Purchase #3 $120.50   8.361%   $130.575   $130.58   $130.60   $130.60  
  Purchase #4 $92.43   13.103%   $104.5411   $104.54   $104.55   $104.50  
  Purchase #5 $119.66   13.471%   $135.7794   $135.78   $135.80   $135.80  
  Purchase #6 $33.41   7.578%   $35.9418   $35.94   $35.95   $35.90  
  Purchase #7 $156.61   5.870%   $165.803   $165.80   $165.80   $165.80  
  7 purchase totals = $896.14       $982.0525   $982.06   $982.10   $982.00