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 $51.41   12.715%   $57.9468   $57.95   $57.95   $57.90  
  Purchase #2 $207.54   7.134%   $222.3459   $222.35   $222.35   $222.30  
  Purchase #3 $54.91   11.324%   $61.128   $61.13   $61.15   $61.10  
  Purchase #4 $58.50   11.740%   $65.3679   $65.37   $65.35   $65.40  
  Purchase #5 $230.45   10.116%   $253.7623   $253.76   $253.75   $253.80  
  Purchase #6 $196.52   7.659%   $211.5715   $211.57   $211.55   $211.60  
  Purchase #7 $226.86   11.844%   $253.7293   $253.73   $253.75   $253.70  
  7 purchase totals = $1,026.19       $1,125.8517   $1,125.86   $1,125.85   $1,125.80