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 $64.73   5.108%   $68.0364   $68.04   $68.05   $68.00  
  Purchase #2 $129.98   3.468%   $134.4877   $134.49   $134.50   $134.50  
  Purchase #3 $211.28   3.187%   $218.0135   $218.01   $218.00   $218.00  
  Purchase #4 $167.51   6.310%   $178.0799   $178.08   $178.10   $178.10  
  Purchase #5 $182.56   5.719%   $193.0006   $193.00   $193.00   $193.00  
  Purchase #6 $5.52   3.135%   $5.6931   $5.69   $5.70   $5.70  
  Purchase #7 $224.49   10.601%   $248.2882   $248.29   $248.30   $248.30  
  7 purchase totals = $986.07       $1,045.5994   $1,045.60   $1,045.65   $1,045.60