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 $240.90   8.755%   $261.9908   $261.99   $262.00   $262.00  
  Purchase #2 $137.48   4.269%   $143.349   $143.35   $143.35   $143.30  
  Purchase #3 $121.35   7.435%   $130.3724   $130.37   $130.35   $130.40  
  Purchase #4 $103.85   6.451%   $110.5494   $110.55   $110.55   $110.50  
  Purchase #5 $231.59   5.152%   $243.5215   $243.52   $243.50   $243.50  
  Purchase #6 $131.74   8.253%   $142.6125   $142.61   $142.60   $142.60  
  Purchase #7 $83.61   12.440%   $94.0111   $94.01   $94.00   $94.00  
  7 purchase totals = $1,050.52       $1,126.4067   $1,126.40   $1,126.35   $1,126.30