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 $176.81   9.274%   $193.2074   $193.21   $193.20   $193.20  
  Purchase #2 $180.49   8.814%   $196.3984   $196.40   $196.40   $196.40  
  Purchase #3 $96.74   7.303%   $103.8049   $103.80   $103.80   $103.80  
  Purchase #4 $187.74   8.661%   $204.0002   $204.00   $204.00   $204.00  
  Purchase #5 $183.55   12.517%   $206.525   $206.53   $206.55   $206.50  
  Purchase #6 $7.85   3.568%   $8.1301   $8.13   $8.15   $8.10  
  Purchase #7 $239.42   10.197%   $263.8337   $263.83   $263.85   $263.80  
  7 purchase totals = $1,072.60       $1,175.8997   $1,175.90   $1,175.95   $1,175.80