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 $58.51   11.334%   $65.1415   $65.14   $65.15   $65.10  
  Purchase #2 $195.72   9.138%   $213.6049   $213.60   $213.60   $213.60  
  Purchase #3 $126.85   4.275%   $132.2728   $132.27   $132.25   $132.30  
  Purchase #4 $243.57   12.197%   $273.2782   $273.28   $273.30   $273.30  
  Purchase #5 $139.26   12.126%   $156.1467   $156.15   $156.15   $156.10  
  Purchase #6 $152.50   7.138%   $163.3855   $163.39   $163.40   $163.40  
  Purchase #7 $59.72   6.349%   $63.5116   $63.51   $63.50   $63.50  
  7 purchase totals = $976.13       $1,067.3412   $1,067.34   $1,067.35   $1,067.30