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 $215.88   9.788%   $237.0103   $237.01   $237.00   $237.00  
  Purchase #2 $186.85   4.704%   $195.6394   $195.64   $195.65   $195.60  
  Purchase #3 $15.50   12.369%   $17.4172   $17.42   $17.40   $17.40  
  Purchase #4 $92.80   3.511%   $96.0582   $96.06   $96.05   $96.10  
  Purchase #5 $168.40   4.391%   $175.7944   $175.79   $175.80   $175.80  
  Purchase #6 $65.50   11.512%   $73.0404   $73.04   $73.05   $73.00  
  Purchase #7 $237.55   10.776%   $263.1484   $263.15   $263.15   $263.10  
  7 purchase totals = $982.48       $1,058.1083   $1,058.11   $1,058.10   $1,058.00