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 $194.53   3.473%   $201.286   $201.29   $201.30   $201.30  
  Purchase #2 $239.51   6.862%   $255.9452   $255.95   $255.95   $255.90  
  Purchase #3 $98.41   10.572%   $108.8139   $108.81   $108.80   $108.80  
  Purchase #4 $150.86   3.363%   $155.9334   $155.93   $155.95   $155.90  
  Purchase #5 $161.75   9.384%   $176.9286   $176.93   $176.95   $176.90  
  Purchase #6 $43.27   13.116%   $48.9453   $48.95   $48.95   $48.90  
  Purchase #7 $210.44   12.667%   $237.0964   $237.10   $237.10   $237.10  
  7 purchase totals = $1,098.77       $1,184.9488   $1,184.96   $1,185.00   $1,184.80