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 $88.56   8.383%   $95.984   $95.98   $96.00   $96.00  
  Purchase #2 $72.45   9.707%   $79.4827   $79.48   $79.50   $79.50  
  Purchase #3 $76.70   8.615%   $83.3077   $83.31   $83.30   $83.30  
  Purchase #4 $190.51   11.641%   $212.6873   $212.69   $212.70   $212.70  
  Purchase #5 $53.42   8.709%   $58.0723   $58.07   $58.05   $58.10  
  Purchase #6 $128.30   8.843%   $139.6456   $139.65   $139.65   $139.60  
  Purchase #7 $183.85   10.663%   $203.4539   $203.45   $203.45   $203.50  
  7 purchase totals = $793.79       $872.6335   $872.63   $872.65   $872.70