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 $182.77   10.503%   $201.9663   $201.97   $201.95   $202.00  
  Purchase #2 $66.42   7.720%   $71.5476   $71.55   $71.55   $71.50  
  Purchase #3 $238.73   12.175%   $267.7954   $267.80   $267.80   $267.80  
  Purchase #4 $126.31   11.239%   $140.506   $140.51   $140.50   $140.50  
  Purchase #5 $152.50   12.546%   $171.6327   $171.63   $171.65   $171.60  
  Purchase #6 $186.93   4.536%   $195.4091   $195.41   $195.40   $195.40  
  Purchase #7 $122.50   3.146%   $126.3539   $126.35   $126.35   $126.40  
  7 purchase totals = $1,076.16       $1,175.2110   $1,175.22   $1,175.20   $1,175.20