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 $86.58   9.379%   $94.7003   $94.70   $94.70   $94.70  
  Purchase #2 $90.71   8.193%   $98.1419   $98.14   $98.15   $98.10  
  Purchase #3 $145.45   11.778%   $162.5811   $162.58   $162.60   $162.60  
  Purchase #4 $56.53   3.614%   $58.573   $58.57   $58.55   $58.60  
  Purchase #5 $121.48   4.784%   $127.2916   $127.29   $127.30   $127.30  
  Purchase #6 $229.39   13.606%   $260.6008   $260.60   $260.60   $260.60  
  Purchase #7 $145.51   7.514%   $156.4436   $156.44   $156.45   $156.40  
  7 purchase totals = $875.65       $958.3323   $958.32   $958.35   $958.30