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 $192.51   10.758%   $213.2202   $213.22   $213.20   $213.20  
  Purchase #2 $226.30   11.506%   $252.3381   $252.34   $252.35   $252.30  
  Purchase #3 $59.80   3.647%   $61.9809   $61.98   $62.00   $62.00  
  Purchase #4 $210.57   9.556%   $230.6921   $230.69   $230.70   $230.70  
  Purchase #5 $28.98   9.838%   $31.8311   $31.83   $31.85   $31.80  
  Purchase #6 $106.44   11.808%   $119.0084   $119.01   $119.00   $119.00  
  Purchase #7 $55.82   3.841%   $57.964   $57.96   $57.95   $58.00  
  7 purchase totals = $880.42       $967.0348   $967.03   $967.05   $967.00