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 $211.26   11.520%   $235.5972   $235.60   $235.60   $235.60  
  Purchase #2 $67.95   10.220%   $74.8945   $74.89   $74.90   $74.90  
  Purchase #3 $8.50   4.198%   $8.8568   $8.86   $8.85   $8.90  
  Purchase #4 $29.29   13.818%   $33.3373   $33.34   $33.35   $33.30  
  Purchase #5 $149.49   12.409%   $168.0402   $168.04   $168.05   $168.00  
  Purchase #6 $195.79   11.355%   $218.022   $218.02   $218.00   $218.00  
  Purchase #7 $231.29   11.139%   $257.0534   $257.05   $257.05   $257.10  
  7 purchase totals = $893.57       $995.8014   $995.80   $995.80   $995.80