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 $54.31   6.114%   $57.6305   $57.63   $57.65   $57.60  
  Purchase #2 $182.97   13.347%   $207.391   $207.39   $207.40   $207.40  
  Purchase #3 $220.26   3.226%   $227.3656   $227.37   $227.35   $227.40  
  Purchase #4 $185.53   4.206%   $193.3334   $193.33   $193.35   $193.30  
  Purchase #5 $45.82   6.757%   $48.9161   $48.92   $48.90   $48.90  
  Purchase #6 $174.79   5.710%   $184.7705   $184.77   $184.75   $184.80  
  Purchase #7 $195.79   6.118%   $207.7684   $207.77   $207.75   $207.80  
  7 purchase totals = $1,059.47       $1,127.1755   $1,127.18   $1,127.15   $1,127.20