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 $181.32   7.421%   $194.7758   $194.78   $194.80   $194.80  
  Purchase #2 $221.61   7.782%   $238.8557   $238.86   $238.85   $238.90  
  Purchase #3 $177.93   3.371%   $183.928   $183.93   $183.95   $183.90  
  Purchase #4 $90.45   5.174%   $95.1299   $95.13   $95.15   $95.10  
  Purchase #5 $178.34   9.537%   $195.3483   $195.35   $195.35   $195.30  
  Purchase #6 $138.96   11.417%   $154.8251   $154.83   $154.85   $154.80  
  Purchase #7 $136.92   4.238%   $142.7227   $142.72   $142.70   $142.70  
  7 purchase totals = $1,125.53       $1,205.5855   $1,205.60   $1,205.65   $1,205.50