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 $153.84   7.633%   $165.5826   $165.58   $165.60   $165.60  
  Purchase #2 $175.77   5.103%   $184.7395   $184.74   $184.75   $184.70  
  Purchase #3 $49.53   7.815%   $53.4008   $53.40   $53.40   $53.40  
  Purchase #4 $187.66   13.397%   $212.8008   $212.80   $212.80   $212.80  
  Purchase #5 $231.88   5.400%   $244.4015   $244.40   $244.40   $244.40  
  Purchase #6 $74.29   4.169%   $77.3872   $77.39   $77.40   $77.40  
  Purchase #7 $206.57   6.757%   $220.5279   $220.53   $220.55   $220.50  
  7 purchase totals = $1,079.54       $1,158.8403   $1,158.84   $1,158.90   $1,158.80