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 $241.70   8.486%   $262.2107   $262.21   $262.20   $262.20  
  Purchase #2 $79.54   6.301%   $84.5518   $84.55   $84.55   $84.60  
  Purchase #3 $218.51   9.279%   $238.7855   $238.79   $238.80   $238.80  
  Purchase #4 $213.97   13.410%   $242.6634   $242.66   $242.65   $242.70  
  Purchase #5 $40.65   10.828%   $45.0516   $45.05   $45.05   $45.10  
  Purchase #6 $157.65   9.309%   $172.3256   $172.33   $172.35   $172.30  
  Purchase #7 $61.73   4.703%   $64.6332   $64.63   $64.65   $64.60  
  7 purchase totals = $1,013.75       $1,110.2218   $1,110.22   $1,110.25   $1,110.30