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 $93.49   13.731%   $106.3271   $106.33   $106.35   $106.30  
  Purchase #2 $23.73   6.774%   $25.3375   $25.34   $25.35   $25.30  
  Purchase #3 $19.66   12.744%   $22.1655   $22.17   $22.15   $22.20  
  Purchase #4 $57.38   3.218%   $59.2265   $59.23   $59.25   $59.20  
  Purchase #5 $101.94   6.487%   $108.5528   $108.55   $108.55   $108.60  
  Purchase #6 $217.32   13.679%   $247.0472   $247.05   $247.05   $247.00  
  Purchase #7 $181.50   7.665%   $195.412   $195.41   $195.40   $195.40  
  7 purchase totals = $695.02       $764.0686   $764.08   $764.10   $764.00