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 $46.76   5.245%   $49.2126   $49.21   $49.20   $49.20  
  Purchase #2 $203.99   3.764%   $211.6682   $211.67   $211.65   $211.70  
  Purchase #3 $248.84   5.730%   $263.0985   $263.10   $263.10   $263.10  
  Purchase #4 $69.82   5.165%   $73.4262   $73.43   $73.45   $73.40  
  Purchase #5 $145.62   10.796%   $161.3411   $161.34   $161.35   $161.30  
  Purchase #6 $114.69   7.122%   $122.8582   $122.86   $122.85   $122.90  
  Purchase #7 $243.93   10.337%   $269.145   $269.15   $269.15   $269.10  
  7 purchase totals = $1,073.65       $1,150.7498   $1,150.76   $1,150.75   $1,150.70