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 $195.96   11.777%   $219.0382   $219.04   $219.05   $219.00  
  Purchase #2 $117.44   9.506%   $128.6038   $128.60   $128.60   $128.60  
  Purchase #3 $62.82   8.433%   $68.1176   $68.12   $68.10   $68.10  
  Purchase #4 $26.73   3.444%   $27.6506   $27.65   $27.65   $27.70  
  Purchase #5 $152.38   12.383%   $171.2492   $171.25   $171.25   $171.20  
  Purchase #6 $195.63   12.445%   $219.9762   $219.98   $220.00   $220.00  
  Purchase #7 $132.99   6.762%   $141.9828   $141.98   $142.00   $142.00  
  7 purchase totals = $883.95       $976.6184   $976.62   $976.65   $976.60