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 $144.70   5.511%   $152.6744   $152.67   $152.65   $152.70  
  Purchase #2 $237.41   5.562%   $250.6147   $250.61   $250.60   $250.60  
  Purchase #3 $24.49   11.423%   $27.2875   $27.29   $27.30   $27.30  
  Purchase #4 $43.61   13.286%   $49.404   $49.40   $49.40   $49.40  
  Purchase #5 $42.81   9.172%   $46.7365   $46.74   $46.75   $46.70  
  Purchase #6 $16.69   11.657%   $18.6356   $18.64   $18.65   $18.60  
  Purchase #7 $195.37   3.394%   $202.0009   $202.00   $202.00   $202.00  
  7 purchase totals = $705.08       $747.3536   $747.35   $747.35   $747.30