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 $191.88   10.517%   $212.06   $212.06   $212.05   $212.10  
  Purchase #2 $230.32   5.408%   $242.7757   $242.78   $242.80   $242.80  
  Purchase #3 $62.55   13.406%   $70.9355   $70.94   $70.95   $70.90  
  Purchase #4 $232.81   13.162%   $263.4525   $263.45   $263.45   $263.50  
  Purchase #5 $238.63   3.762%   $247.6073   $247.61   $247.60   $247.60  
  Purchase #6 $185.67   4.547%   $194.1124   $194.11   $194.10   $194.10  
  Purchase #7 $62.58   12.459%   $70.3768   $70.38   $70.40   $70.40  
  7 purchase totals = $1,204.44       $1,301.3202   $1,301.33   $1,301.35   $1,301.40