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 $114.98   11.112%   $127.7566   $127.76   $127.75   $127.80  
  Purchase #2 $195.46   12.125%   $219.1595   $219.16   $219.15   $219.20  
  Purchase #3 $151.36   6.196%   $160.7383   $160.74   $160.75   $160.70  
  Purchase #4 $50.34   10.556%   $55.6539   $55.65   $55.65   $55.70  
  Purchase #5 $220.60   8.755%   $239.9135   $239.91   $239.90   $239.90  
  Purchase #6 $193.88   6.126%   $205.7571   $205.76   $205.75   $205.80  
  Purchase #7 $83.76   3.687%   $86.8482   $86.85   $86.85   $86.80  
  7 purchase totals = $1,010.38       $1,095.8271   $1,095.83   $1,095.80   $1,095.90