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 $96.86   9.701%   $106.2564   $106.26   $106.25   $106.30  
  Purchase #2 $131.67   11.416%   $146.7014   $146.70   $146.70   $146.70  
  Purchase #3 $33.30   10.556%   $36.8151   $36.82   $36.80   $36.80  
  Purchase #4 $95.75   9.253%   $104.6097   $104.61   $104.60   $104.60  
  Purchase #5 $163.94   10.802%   $181.6488   $181.65   $181.65   $181.60  
  Purchase #6 $49.26   3.598%   $51.0324   $51.03   $51.05   $51.00  
  Purchase #7 $136.99   13.706%   $155.7658   $155.77   $155.75   $155.80  
  7 purchase totals = $707.77       $782.8296   $782.84   $782.80   $782.80