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 $33.95   6.621%   $36.1978   $36.20   $36.20   $36.20  
  Purchase #2 $168.47   10.224%   $185.6944   $185.69   $185.70   $185.70  
  Purchase #3 $153.97   13.811%   $175.2348   $175.23   $175.25   $175.20  
  Purchase #4 $178.26   7.857%   $192.2659   $192.27   $192.25   $192.30  
  Purchase #5 $234.26   8.830%   $254.9452   $254.95   $254.95   $254.90  
  Purchase #6 $23.29   11.471%   $25.9616   $25.96   $25.95   $26.00  
  Purchase #7 $241.48   9.707%   $264.9205   $264.92   $264.90   $264.90  
  7 purchase totals = $1,033.68       $1,135.2202   $1,135.22   $1,135.20   $1,135.20