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 $65.41   10.756%   $72.4455   $72.45   $72.45   $72.40  
  Purchase #2 $40.82   13.343%   $46.2666   $46.27   $46.25   $46.30  
  Purchase #3 $69.70   10.480%   $77.0046   $77.00   $77.00   $77.00  
  Purchase #4 $141.55   4.246%   $147.5602   $147.56   $147.55   $147.60  
  Purchase #5 $40.90   9.212%   $44.6677   $44.67   $44.65   $44.70  
  Purchase #6 $196.91   6.371%   $209.4551   $209.46   $209.45   $209.50  
  Purchase #7 $160.54   4.547%   $167.8398   $167.84   $167.85   $167.80  
  7 purchase totals = $715.83       $765.2395   $765.25   $765.20   $765.30