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 $60.71   10.310%   $66.9692   $66.97   $66.95   $67.00  
  Purchase #2 $224.77   7.199%   $240.9512   $240.95   $240.95   $241.00  
  Purchase #3 $150.87   4.640%   $157.8704   $157.87   $157.85   $157.90  
  Purchase #4 $105.28   3.300%   $108.7542   $108.75   $108.75   $108.80  
  Purchase #5 $190.98   12.515%   $214.8811   $214.88   $214.90   $214.90  
  Purchase #6 $127.83   6.256%   $135.827   $135.83   $135.85   $135.80  
  Purchase #7 $243.44   9.703%   $267.061   $267.06   $267.05   $267.10  
  7 purchase totals = $1,103.88       $1,192.3141   $1,192.31   $1,192.30   $1,192.50