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 $87.92   6.872%   $93.9619   $93.96   $93.95   $94.00  
  Purchase #2 $241.75   3.531%   $250.2862   $250.29   $250.30   $250.30  
  Purchase #3 $31.80   13.121%   $35.9725   $35.97   $35.95   $36.00  
  Purchase #4 $219.67   9.231%   $239.9477   $239.95   $239.95   $239.90  
  Purchase #5 $225.99   13.240%   $255.9111   $255.91   $255.90   $255.90  
  Purchase #6 $137.90   7.866%   $148.7472   $148.75   $148.75   $148.70  
  Purchase #7 $130.37   13.245%   $147.6375   $147.64   $147.65   $147.60  
  7 purchase totals = $1,075.40       $1,172.4641   $1,172.47   $1,172.45   $1,172.40