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 $194.41   5.228%   $204.5738   $204.57   $204.55   $204.60  
  Purchase #2 $246.39   6.451%   $262.2846   $262.28   $262.30   $262.30  
  Purchase #3 $54.50   8.234%   $58.9875   $58.99   $59.00   $59.00  
  Purchase #4 $170.84   3.547%   $176.8997   $176.90   $176.90   $176.90  
  Purchase #5 $164.37   12.307%   $184.599   $184.60   $184.60   $184.60  
  Purchase #6 $33.44   8.642%   $36.3299   $36.33   $36.35   $36.30  
  Purchase #7 $110.59   13.218%   $125.2078   $125.21   $125.20   $125.20  
  7 purchase totals = $974.54       $1,048.8823   $1,048.88   $1,048.90   $1,048.90