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 $196.28   5.485%   $207.046   $207.05   $207.05   $207.00  
  Purchase #2 $145.35   5.243%   $152.9707   $152.97   $152.95   $153.00  
  Purchase #3 $239.39   10.189%   $263.7814   $263.78   $263.80   $263.80  
  Purchase #4 $47.47   5.288%   $49.9802   $49.98   $50.00   $50.00  
  Purchase #5 $65.44   4.626%   $68.4673   $68.47   $68.45   $68.50  
  Purchase #6 $169.70   5.289%   $178.6754   $178.68   $178.70   $178.70  
  Purchase #7 $87.87   5.720%   $92.8962   $92.90   $92.90   $92.90  
  7 purchase totals = $951.50       $1,013.8172   $1,013.83   $1,013.85   $1,013.90