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 $43.36   13.671%   $49.2877   $49.29   $49.30   $49.30  
  Purchase #2 $176.61   12.479%   $198.6492   $198.65   $198.65   $198.60  
  Purchase #3 $6.50   6.451%   $6.9193   $6.92   $6.90   $6.90  
  Purchase #4 $45.70   8.534%   $49.6   $49.60   $49.60   $49.60  
  Purchase #5 $110.46   8.460%   $119.8049   $119.80   $119.80   $119.80  
  Purchase #6 $107.71   10.670%   $119.2027   $119.20   $119.20   $119.20  
  Purchase #7 $184.96   10.113%   $203.665   $203.67   $203.65   $203.70  
  7 purchase totals = $675.30       $747.1288   $747.13   $747.10   $747.10