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 $62.62   11.261%   $69.6716   $69.67   $69.65   $69.70  
  Purchase #2 $119.33   5.871%   $126.3359   $126.34   $126.35   $126.30  
  Purchase #3 $148.56   8.286%   $160.8697   $160.87   $160.85   $160.90  
  Purchase #4 $227.61   11.514%   $253.817   $253.82   $253.80   $253.80  
  Purchase #5 $84.53   10.546%   $93.4445   $93.44   $93.45   $93.40  
  Purchase #6 $141.59   3.692%   $146.8175   $146.82   $146.80   $146.80  
  Purchase #7 $142.27   6.861%   $152.0311   $152.03   $152.05   $152.00  
  7 purchase totals = $926.51       $1,002.9873   $1,002.99   $1,002.95   $1,002.90