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 $62.57   11.786%   $69.9445   $69.94   $69.95   $69.90  
  Purchase #2 $141.38   7.732%   $152.3115   $152.31   $152.30   $152.30  
  Purchase #3 $61.72   10.742%   $68.35   $68.35   $68.35   $68.40  
  Purchase #4 $162.86   9.599%   $178.4929   $178.49   $178.50   $178.50  
  Purchase #5 $87.77   3.185%   $90.5655   $90.57   $90.55   $90.60  
  Purchase #6 $213.64   8.187%   $231.1307   $231.13   $231.15   $231.10  
  Purchase #7 $171.36   11.585%   $191.2121   $191.21   $191.20   $191.20  
  7 purchase totals = $901.30       $982.0072   $982.00   $982.00   $982.00