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 $62.37   4.695%   $65.2983   $65.30   $65.30   $65.30  
  Purchase #2 $95.67   13.720%   $108.7959   $108.80   $108.80   $108.80  
  Purchase #3 $233.96   5.711%   $247.3215   $247.32   $247.30   $247.30  
  Purchase #4 $29.54   5.113%   $31.0504   $31.05   $31.05   $31.10  
  Purchase #5 $237.44   13.713%   $270.0001   $270.00   $270.00   $270.00  
  Purchase #6 $160.72   13.439%   $182.3192   $182.32   $182.30   $182.30  
  Purchase #7 $238.88   12.527%   $268.8045   $268.80   $268.80   $268.80  
  7 purchase totals = $1,058.58       $1,173.5899   $1,173.59   $1,173.55   $1,173.60