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 $57.51   6.499%   $61.2476   $61.25   $61.25   $61.20  
  Purchase #2 $103.89   8.407%   $112.624   $112.62   $112.60   $112.60  
  Purchase #3 $187.90   3.220%   $193.9504   $193.95   $193.95   $194.00  
  Purchase #4 $238.81   10.181%   $263.1232   $263.12   $263.10   $263.10  
  Purchase #5 $203.53   4.607%   $212.9066   $212.91   $212.90   $212.90  
  Purchase #6 $135.80   7.172%   $145.5396   $145.54   $145.55   $145.50  
  Purchase #7 $196.65   11.413%   $219.0937   $219.09   $219.10   $219.10  
  7 purchase totals = $1,124.09       $1,208.4851   $1,208.48   $1,208.45   $1,208.40