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 $88.61   7.712%   $95.4436   $95.44   $95.45   $95.40  
  Purchase #2 $156.41   11.264%   $174.028   $174.03   $174.05   $174.00  
  Purchase #3 $138.57   3.169%   $142.9613   $142.96   $142.95   $143.00  
  Purchase #4 $132.51   11.308%   $147.4942   $147.49   $147.50   $147.50  
  Purchase #5 $217.38   4.615%   $227.4121   $227.41   $227.40   $227.40  
  Purchase #6 $116.57   11.540%   $130.0222   $130.02   $130.00   $130.00  
  Purchase #7 $33.96   8.552%   $36.8643   $36.86   $36.85   $36.90  
  7 purchase totals = $884.01       $954.2257   $954.21   $954.20   $954.20