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 $211.34   9.635%   $231.7026   $231.70   $231.70   $231.70  
  Purchase #2 $87.48   6.266%   $92.9615   $92.96   $92.95   $93.00  
  Purchase #3 $244.97   6.831%   $261.7039   $261.70   $261.70   $261.70  
  Purchase #4 $13.68   10.229%   $15.0793   $15.08   $15.10   $15.10  
  Purchase #5 $72.80   8.350%   $78.8788   $78.88   $78.90   $78.90  
  Purchase #6 $151.60   4.215%   $157.9899   $157.99   $158.00   $158.00  
  Purchase #7 $220.84   4.413%   $230.5857   $230.59   $230.60   $230.60  
  7 purchase totals = $1,002.71       $1,068.9017   $1,068.90   $1,068.95   $1,069.00