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 $173.92   6.197%   $184.6978   $184.70   $184.70   $184.70  
  Purchase #2 $168.93   5.137%   $177.6079   $177.61   $177.60   $177.60  
  Purchase #3 $44.57   8.360%   $48.2961   $48.30   $48.30   $48.30  
  Purchase #4 $169.82   10.599%   $187.8192   $187.82   $187.80   $187.80  
  Purchase #5 $179.32   8.217%   $194.0547   $194.05   $194.05   $194.10  
  Purchase #6 $233.50   4.766%   $244.6286   $244.63   $244.65   $244.60  
  Purchase #7 $185.47   6.839%   $198.1543   $198.15   $198.15   $198.20  
  7 purchase totals = $1,155.53       $1,235.2586   $1,235.26   $1,235.25   $1,235.30