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 $211.29   6.643%   $225.326   $225.33   $225.35   $225.30  
  Purchase #2 $184.64   9.424%   $202.0405   $202.04   $202.05   $202.00  
  Purchase #3 $62.75   12.545%   $70.622   $70.62   $70.60   $70.60  
  Purchase #4 $244.66   8.773%   $266.124   $266.12   $266.10   $266.10  
  Purchase #5 $233.28   12.342%   $262.0714   $262.07   $262.05   $262.10  
  Purchase #6 $178.73   12.689%   $201.409   $201.41   $201.40   $201.40  
  Purchase #7 $88.36   11.464%   $98.4896   $98.49   $98.50   $98.50  
  7 purchase totals = $1,203.71       $1,326.0825   $1,326.08   $1,326.05   $1,326.00