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 $246.67   7.534%   $265.2541   $265.25   $265.25   $265.30  
  Purchase #2 $95.35   3.144%   $98.3478   $98.35   $98.35   $98.30  
  Purchase #3 $34.37   9.806%   $37.7403   $37.74   $37.75   $37.70  
  Purchase #4 $151.87   9.119%   $165.719   $165.72   $165.70   $165.70  
  Purchase #5 $232.78   8.620%   $252.8456   $252.85   $252.85   $252.80  
  Purchase #6 $232.46   5.625%   $245.5359   $245.54   $245.55   $245.50  
  Purchase #7 $75.58   13.738%   $85.9632   $85.96   $85.95   $86.00  
  7 purchase totals = $1,069.08       $1,151.4059   $1,151.41   $1,151.40   $1,151.30