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 $214.58   7.487%   $230.6456   $230.65   $230.65   $230.60  
  Purchase #2 $69.87   5.370%   $73.622   $73.62   $73.60   $73.60  
  Purchase #3 $111.91   7.809%   $120.6491   $120.65   $120.65   $120.60  
  Purchase #4 $132.72   12.660%   $149.5224   $149.52   $149.50   $149.50  
  Purchase #5 $148.38   5.866%   $157.084   $157.08   $157.10   $157.10  
  Purchase #6 $174.70   12.687%   $196.8642   $196.86   $196.85   $196.90  
  Purchase #7 $186.71   5.238%   $196.4899   $196.49   $196.50   $196.50  
  7 purchase totals = $1,038.87       $1,124.8772   $1,124.87   $1,124.85   $1,124.80