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 $38.81   12.690%   $43.735   $43.74   $43.75   $43.70  
  Purchase #2 $208.35   8.153%   $225.3368   $225.34   $225.35   $225.30  
  Purchase #3 $65.71   11.512%   $73.2745   $73.27   $73.25   $73.30  
  Purchase #4 $30.88   11.283%   $34.3642   $34.36   $34.35   $34.40  
  Purchase #5 $208.27   12.106%   $233.4832   $233.48   $233.50   $233.50  
  Purchase #6 $191.40   6.341%   $203.5367   $203.54   $203.55   $203.50  
  Purchase #7 $65.26   10.684%   $72.2324   $72.23   $72.25   $72.20  
  7 purchase totals = $808.68       $885.9628   $885.96   $886.00   $885.90