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 $193.59   6.756%   $206.6689   $206.67   $206.65   $206.70  
  Purchase #2 $196.28   5.604%   $207.2795   $207.28   $207.30   $207.30  
  Purchase #3 $33.56   13.251%   $38.007   $38.01   $38.00   $38.00  
  Purchase #4 $123.50   8.337%   $133.7962   $133.80   $133.80   $133.80  
  Purchase #5 $67.42   11.374%   $75.0884   $75.09   $75.10   $75.10  
  Purchase #6 $183.31   6.706%   $195.6028   $195.60   $195.60   $195.60  
  Purchase #7 $181.38   11.200%   $201.6946   $201.69   $201.70   $201.70  
  7 purchase totals = $979.04       $1,058.1374   $1,058.14   $1,058.15   $1,058.20