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 $214.75   6.638%   $229.0051   $229.01   $229.00   $229.00  
  Purchase #2 $202.35   4.645%   $211.7492   $211.75   $211.75   $211.70  
  Purchase #3 $230.44   10.420%   $254.4518   $254.45   $254.45   $254.50  
  Purchase #4 $50.82   11.139%   $56.4808   $56.48   $56.50   $56.50  
  Purchase #5 $206.60   9.786%   $226.8179   $226.82   $226.80   $226.80  
  Purchase #6 $218.67   12.647%   $246.3252   $246.33   $246.35   $246.30  
  Purchase #7 $242.94   7.562%   $261.3111   $261.31   $261.30   $261.30  
  7 purchase totals = $1,366.57       $1,486.1411   $1,486.15   $1,486.15   $1,486.10