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 $44.38   4.477%   $46.3669   $46.37   $46.35   $46.40  
  Purchase #2 $168.64   10.331%   $186.0622   $186.06   $186.05   $186.10  
  Purchase #3 $120.71   3.428%   $124.8479   $124.85   $124.85   $124.80  
  Purchase #4 $42.54   12.731%   $47.9558   $47.96   $47.95   $48.00  
  Purchase #5 $219.86   5.617%   $232.2095   $232.21   $232.20   $232.20  
  Purchase #6 $250.28   11.102%   $278.0661   $278.07   $278.05   $278.10  
  Purchase #7 $242.97   9.840%   $266.8782   $266.88   $266.90   $266.90  
  7 purchase totals = $1,089.38       $1,182.3866   $1,182.40   $1,182.35   $1,182.50