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 $122.99   3.512%   $127.3094   $127.31   $127.30   $127.30  
  Purchase #2 $144.54   3.673%   $149.849   $149.85   $149.85   $149.80  
  Purchase #3 $131.48   7.821%   $141.7631   $141.76   $141.75   $141.80  
  Purchase #4 $216.51   4.796%   $226.8938   $226.89   $226.90   $226.90  
  Purchase #5 $87.56   6.636%   $93.3705   $93.37   $93.35   $93.40  
  Purchase #6 $249.52   4.247%   $260.1171   $260.12   $260.10   $260.10  
  Purchase #7 $14.54   4.607%   $15.2099   $15.21   $15.20   $15.20  
  7 purchase totals = $967.14       $1,014.5128   $1,014.51   $1,014.45   $1,014.50