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 $87.82   8.246%   $95.0616   $95.06   $95.05   $95.10  
  Purchase #2 $31.58   10.408%   $34.8668   $34.87   $34.85   $34.90  
  Purchase #3 $104.93   7.783%   $113.0967   $113.10   $113.10   $113.10  
  Purchase #4 $198.68   8.379%   $215.3274   $215.33   $215.35   $215.30  
  Purchase #5 $128.60   4.603%   $134.5195   $134.52   $134.50   $134.50  
  Purchase #6 $10.66   3.237%   $11.0051   $11.01   $11.00   $11.00  
  Purchase #7 $136.26   5.247%   $143.4096   $143.41   $143.40   $143.40  
  7 purchase totals = $698.53       $747.2867   $747.30   $747.25   $747.30