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 $86.81   9.736%   $95.2618   $95.26   $95.25   $95.30  
  Purchase #2 $231.97   13.643%   $263.6177   $263.62   $263.60   $263.60  
  Purchase #3 $36.96   6.352%   $39.3077   $39.31   $39.30   $39.30  
  Purchase #4 $175.64   4.511%   $183.5631   $183.56   $183.55   $183.60  
  Purchase #5 $101.99   12.169%   $114.4012   $114.40   $114.40   $114.40  
  Purchase #6 $212.52   6.664%   $226.6823   $226.68   $226.70   $226.70  
  Purchase #7 $206.62   8.207%   $223.5773   $223.58   $223.60   $223.60  
  7 purchase totals = $1,052.51       $1,146.4111   $1,146.41   $1,146.40   $1,146.50