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 $94.50   12.520%   $106.3314   $106.33   $106.35   $106.30  
  Purchase #2 $203.38   8.354%   $220.3704   $220.37   $220.35   $220.40  
  Purchase #3 $98.36   5.872%   $104.1357   $104.14   $104.15   $104.10  
  Purchase #4 $54.33   11.789%   $60.735   $60.74   $60.75   $60.70  
  Purchase #5 $248.46   11.513%   $277.0652   $277.07   $277.05   $277.10  
  Purchase #6 $206.54   10.169%   $227.5431   $227.54   $227.55   $227.50  
  Purchase #7 $16.79   6.781%   $17.9285   $17.93   $17.95   $17.90  
  7 purchase totals = $922.36       $1,014.1093   $1,014.12   $1,014.15   $1,014.00