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 $187.55   3.470%   $194.058   $194.06   $194.05   $194.10  
  Purchase #2 $71.45   6.358%   $75.9928   $75.99   $76.00   $76.00  
  Purchase #3 $177.54   9.156%   $193.7956   $193.80   $193.80   $193.80  
  Purchase #4 $164.73   7.523%   $177.1226   $177.12   $177.10   $177.10  
  Purchase #5 $130.95   9.794%   $143.7752   $143.78   $143.80   $143.80  
  Purchase #6 $175.48   3.844%   $182.2255   $182.23   $182.25   $182.20  
  Purchase #7 $173.95   11.702%   $194.3056   $194.31   $194.30   $194.30  
  7 purchase totals = $1,081.65       $1,161.2753   $1,161.29   $1,161.30   $1,161.30