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 $87.85   11.638%   $98.074   $98.07   $98.05   $98.10  
  Purchase #2 $105.51   8.754%   $114.7463   $114.75   $114.75   $114.70  
  Purchase #3 $107.88   13.595%   $122.5463   $122.55   $122.55   $122.50  
  Purchase #4 $96.60   9.214%   $105.5007   $105.50   $105.50   $105.50  
  Purchase #5 $165.26   4.363%   $172.4703   $172.47   $172.45   $172.50  
  Purchase #6 $249.45   13.802%   $283.8791   $283.88   $283.90   $283.90  
  Purchase #7 $140.52   12.429%   $157.9852   $157.99   $158.00   $158.00  
  7 purchase totals = $953.07       $1,055.2019   $1,055.21   $1,055.20   $1,055.20