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 $59.54   9.206%   $65.0213   $65.02   $65.00   $65.00  
  Purchase #2 $235.81   7.263%   $252.9369   $252.94   $252.95   $252.90  
  Purchase #3 $175.86   4.774%   $184.2556   $184.26   $184.25   $184.30  
  Purchase #4 $61.82   5.332%   $65.1162   $65.12   $65.10   $65.10  
  Purchase #5 $64.30   4.774%   $67.3697   $67.37   $67.35   $67.40  
  Purchase #6 $182.60   13.474%   $207.2035   $207.20   $207.20   $207.20  
  Purchase #7 $247.73   6.823%   $264.6326   $264.63   $264.65   $264.60  
  7 purchase totals = $1,027.66       $1,106.5358   $1,106.54   $1,106.50   $1,106.50