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 $194.32   6.653%   $207.2481   $207.25   $207.25   $207.20  
  Purchase #2 $49.98   9.153%   $54.5547   $54.55   $54.55   $54.60  
  Purchase #3 $146.71   5.563%   $154.8715   $154.87   $154.85   $154.90  
  Purchase #4 $24.42   13.575%   $27.735   $27.74   $27.75   $27.70  
  Purchase #5 $217.93   4.832%   $228.4604   $228.46   $228.45   $228.50  
  Purchase #6 $210.61   11.853%   $235.5736   $235.57   $235.55   $235.60  
  Purchase #7 $145.61   5.592%   $153.7525   $153.75   $153.75   $153.80  
  7 purchase totals = $989.58       $1,062.1958   $1,062.19   $1,062.15   $1,062.30