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 $146.70   4.681%   $153.567   $153.57   $153.55   $153.60  
  Purchase #2 $131.39   3.150%   $135.5288   $135.53   $135.55   $135.50  
  Purchase #3 $15.58   12.826%   $17.5783   $17.58   $17.60   $17.60  
  Purchase #4 $137.27   13.606%   $155.947   $155.95   $155.95   $155.90  
  Purchase #5 $193.45   8.607%   $210.1002   $210.10   $210.10   $210.10  
  Purchase #6 $212.64   5.285%   $223.878   $223.88   $223.90   $223.90  
  Purchase #7 $54.74   7.497%   $58.8439   $58.84   $58.85   $58.80  
  7 purchase totals = $891.77       $955.4432   $955.45   $955.50   $955.40