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 $212.82   13.250%   $241.0187   $241.02   $241.00   $241.00  
  Purchase #2 $27.86   12.334%   $31.2963   $31.30   $31.30   $31.30  
  Purchase #3 $30.88   7.436%   $33.1762   $33.18   $33.20   $33.20  
  Purchase #4 $174.52   6.536%   $185.9266   $185.93   $185.95   $185.90  
  Purchase #5 $155.83   12.576%   $175.4272   $175.43   $175.45   $175.40  
  Purchase #6 $192.50   9.688%   $211.1494   $211.15   $211.15   $211.10  
  Purchase #7 $224.32   10.604%   $248.1069   $248.11   $248.10   $248.10  
  7 purchase totals = $1,018.73       $1,126.1013   $1,126.12   $1,126.15   $1,126.00