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 $62.65   11.242%   $69.6931   $69.69   $69.70   $69.70  
  Purchase #2 $97.51   12.446%   $109.6461   $109.65   $109.65   $109.60  
  Purchase #3 $132.35   9.624%   $145.0874   $145.09   $145.10   $145.10  
  Purchase #4 $176.89   10.454%   $195.3821   $195.38   $195.40   $195.40  
  Purchase #5 $163.28   9.620%   $178.9875   $178.99   $179.00   $179.00  
  Purchase #6 $37.96   6.279%   $40.3435   $40.34   $40.35   $40.30  
  Purchase #7 $42.83   6.270%   $45.5154   $45.52   $45.50   $45.50  
  7 purchase totals = $713.47       $784.6551   $784.66   $784.70   $784.60