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 $61.86   11.386%   $68.9034   $68.90   $68.90   $68.90  
  Purchase #2 $113.41   13.295%   $128.4879   $128.49   $128.50   $128.50  
  Purchase #3 $85.58   11.715%   $95.6057   $95.61   $95.60   $95.60  
  Purchase #4 $201.47   13.791%   $229.2547   $229.25   $229.25   $229.30  
  Purchase #5 $191.78   5.515%   $202.3567   $202.36   $202.35   $202.40  
  Purchase #6 $115.70   11.155%   $128.6063   $128.61   $128.60   $128.60  
  Purchase #7 $199.91   7.804%   $215.511   $215.51   $215.50   $215.50  
  7 purchase totals = $969.71       $1,068.7257   $1,068.73   $1,068.70   $1,068.80