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 $104.60   9.293%   $114.3205   $114.32   $114.30   $114.30  
  Purchase #2 $250.35   7.564%   $269.2865   $269.29   $269.30   $269.30  
  Purchase #3 $76.63   13.633%   $87.077   $87.08   $87.10   $87.10  
  Purchase #4 $220.43   5.712%   $233.021   $233.02   $233.00   $233.00  
  Purchase #5 $146.54   4.489%   $153.1182   $153.12   $153.10   $153.10  
  Purchase #6 $140.34   8.540%   $152.325   $152.33   $152.35   $152.30  
  Purchase #7 $122.53   10.788%   $135.7485   $135.75   $135.75   $135.70  
  7 purchase totals = $1,061.42       $1,144.8967   $1,144.91   $1,144.90   $1,144.80