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 $85.50   9.514%   $93.6345   $93.63   $93.65   $93.60  
  Purchase #2 $116.92   8.610%   $126.9868   $126.99   $127.00   $127.00  
  Purchase #3 $172.61   10.860%   $191.3554   $191.36   $191.35   $191.40  
  Purchase #4 $171.78   7.293%   $184.3079   $184.31   $184.30   $184.30  
  Purchase #5 $241.36   8.810%   $262.6238   $262.62   $262.60   $262.60  
  Purchase #6 $114.29   7.493%   $122.8537   $122.85   $122.85   $122.90  
  Purchase #7 $47.25   7.617%   $50.849   $50.85   $50.85   $50.80  
  7 purchase totals = $949.71       $1,032.6111   $1,032.61   $1,032.60   $1,032.60