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 $96.81   5.280%   $101.9216   $101.92   $101.90   $101.90  
  Purchase #2 $53.62   8.495%   $58.175   $58.18   $58.20   $58.20  
  Purchase #3 $147.81   8.263%   $160.0235   $160.02   $160.00   $160.00  
  Purchase #4 $223.67   6.627%   $238.4926   $238.49   $238.50   $238.50  
  Purchase #5 $183.93   7.676%   $198.0485   $198.05   $198.05   $198.00  
  Purchase #6 $63.84   3.535%   $66.0967   $66.10   $66.10   $66.10  
  Purchase #7 $49.49   9.705%   $54.293   $54.29   $54.30   $54.30  
  7 purchase totals = $819.17       $877.0509   $877.05   $877.05   $877.00