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 $211.25   11.193%   $234.8952   $234.90   $234.90   $234.90  
  Purchase #2 $144.47   12.556%   $162.6097   $162.61   $162.60   $162.60  
  Purchase #3 $185.30   11.612%   $206.817   $206.82   $206.80   $206.80  
  Purchase #4 $207.29   6.289%   $220.3265   $220.33   $220.35   $220.30  
  Purchase #5 $172.62   9.236%   $188.5632   $188.56   $188.55   $188.60  
  Purchase #6 $127.95   9.614%   $140.2511   $140.25   $140.25   $140.30  
  Purchase #7 $38.65   6.714%   $41.245   $41.25   $41.25   $41.20  
  7 purchase totals = $1,087.53       $1,194.7077   $1,194.72   $1,194.70   $1,194.70