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 $41.41   11.298%   $46.0885   $46.09   $46.10   $46.10  
  Purchase #2 $79.59   6.252%   $84.566   $84.57   $84.55   $84.60  
  Purchase #3 $196.63   4.767%   $206.0034   $206.00   $206.00   $206.00  
  Purchase #4 $224.45   9.853%   $246.5651   $246.57   $246.55   $246.60  
  Purchase #5 $233.57   12.531%   $262.8387   $262.84   $262.85   $262.80  
  Purchase #6 $250.38   4.644%   $262.0076   $262.01   $262.00   $262.00  
  Purchase #7 $245.95   4.427%   $256.8382   $256.84   $256.85   $256.80  
  7 purchase totals = $1,271.98       $1,364.9075   $1,364.92   $1,364.90   $1,364.90