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 $191.51   11.748%   $214.0086   $214.01   $214.00   $214.00  
  Purchase #2 $159.76   9.188%   $174.4387   $174.44   $174.45   $174.40  
  Purchase #3 $141.27   5.356%   $148.8364   $148.84   $148.85   $148.80  
  Purchase #4 $147.27   8.472%   $159.7467   $159.75   $159.75   $159.70  
  Purchase #5 $200.67   5.659%   $212.0259   $212.03   $212.05   $212.00  
  Purchase #6 $129.48   5.559%   $136.6778   $136.68   $136.70   $136.70  
  Purchase #7 $74.48   4.837%   $78.0826   $78.08   $78.10   $78.10  
  7 purchase totals = $1,044.44       $1,123.8167   $1,123.83   $1,123.90   $1,123.70