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 $212.26   10.553%   $234.6598   $234.66   $234.65   $234.70  
  Purchase #2 $217.51   11.253%   $241.9864   $241.99   $242.00   $242.00  
  Purchase #3 $87.66   9.793%   $96.2445   $96.24   $96.25   $96.20  
  Purchase #4 $247.43   8.125%   $267.5337   $267.53   $267.55   $267.50  
  Purchase #5 $212.98   9.860%   $233.9798   $233.98   $234.00   $234.00  
  Purchase #6 $238.59   6.719%   $254.6209   $254.62   $254.60   $254.60  
  Purchase #7 $76.49   6.259%   $81.2775   $81.28   $81.30   $81.30  
  7 purchase totals = $1,292.92       $1,410.3026   $1,410.30   $1,410.35   $1,410.30