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 $113.82   3.719%   $118.053   $118.05   $118.05   $118.10  
  Purchase #2 $221.30   3.636%   $229.3465   $229.35   $229.35   $229.30  
  Purchase #3 $145.80   10.150%   $160.5987   $160.60   $160.60   $160.60  
  Purchase #4 $130.37   5.599%   $137.6694   $137.67   $137.65   $137.70  
  Purchase #5 $34.53   3.751%   $35.8252   $35.83   $35.85   $35.80  
  Purchase #6 $211.98   9.357%   $231.815   $231.82   $231.80   $231.80  
  Purchase #7 $96.90   4.489%   $101.2498   $101.25   $101.25   $101.20  
  7 purchase totals = $954.70       $1,014.5576   $1,014.57   $1,014.55   $1,014.50