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 $61.70   11.725%   $68.9343   $68.93   $68.95   $68.90  
  Purchase #2 $82.56   3.729%   $85.6387   $85.64   $85.65   $85.60  
  Purchase #3 $66.65   7.355%   $71.5521   $71.55   $71.55   $71.60  
  Purchase #4 $68.64   10.840%   $76.0806   $76.08   $76.10   $76.10  
  Purchase #5 $102.59   4.271%   $106.9716   $106.97   $106.95   $107.00  
  Purchase #6 $55.50   9.356%   $60.6926   $60.69   $60.70   $60.70  
  Purchase #7 $245.81   3.823%   $255.2073   $255.21   $255.20   $255.20  
  7 purchase totals = $683.45       $725.0772   $725.07   $725.10   $725.10