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 $118.93   6.766%   $126.9768   $126.98   $127.00   $127.00  
  Purchase #2 $25.99   6.727%   $27.7383   $27.74   $27.75   $27.70  
  Purchase #3 $246.27   3.563%   $255.0446   $255.04   $255.05   $255.00  
  Purchase #4 $95.28   6.149%   $101.1388   $101.14   $101.15   $101.10  
  Purchase #5 $96.62   4.440%   $100.9099   $100.91   $100.90   $100.90  
  Purchase #6 $33.60   8.704%   $36.5245   $36.52   $36.50   $36.50  
  Purchase #7 $213.47   3.665%   $221.2937   $221.29   $221.30   $221.30  
  7 purchase totals = $830.16       $869.6266   $869.62   $869.65   $869.50