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 $60.36   4.355%   $62.9887   $62.99   $63.00   $63.00  
  Purchase #2 $132.48   6.456%   $141.0329   $141.03   $141.05   $141.00  
  Purchase #3 $44.73   3.678%   $46.3752   $46.38   $46.40   $46.40  
  Purchase #4 $232.32   11.834%   $259.8127   $259.81   $259.80   $259.80  
  Purchase #5 $235.28   11.831%   $263.116   $263.12   $263.10   $263.10  
  Purchase #6 $199.68   8.574%   $216.8006   $216.80   $216.80   $216.80  
  Purchase #7 $144.67   7.210%   $155.1007   $155.10   $155.10   $155.10  
  7 purchase totals = $1,049.52       $1,145.2268   $1,145.23   $1,145.25   $1,145.20