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 $121.88   3.485%   $126.1275   $126.13   $126.15   $126.10  
  Purchase #2 $209.91   12.254%   $235.6324   $235.63   $235.65   $235.60  
  Purchase #3 $10.31   13.328%   $11.6841   $11.68   $11.70   $11.70  
  Purchase #4 $204.43   8.481%   $221.7677   $221.77   $221.75   $221.80  
  Purchase #5 $198.37   4.286%   $206.8721   $206.87   $206.85   $206.90  
  Purchase #6 $57.53   4.367%   $60.0423   $60.04   $60.05   $60.00  
  Purchase #7 $219.29   9.646%   $240.4427   $240.44   $240.45   $240.40  
  7 purchase totals = $1,021.72       $1,102.5688   $1,102.56   $1,102.60   $1,102.50